Nautel ND2000A-02x-xx0 Technical Instructions

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TECHNICAL INSTRUCTIONS

ND2000A - 02x - xx0

RADIOBEACON TRANSMITTER

500 WATTS

(190 kHz to 535 kHz)

NAPE72 Keyer PWB

Original Issue ....................15 October 2004

Change 1...........................15 January 2005

e-mail: support@nautel.com

web: www.nautel.com

Nautel Maine Inc. Nautel Limited 201 Target Industrial Circle, 10089 Peggy’s Cove Road Bangor, Maine USA 04401 Hackett’s Cove, NS Canada B3Z 3J4 Phone: (207) 947-8200 Phone: (902) 823-3900 Fax: (207) 947-3693 Fax: (902) 823-3183

ISO 9002 REGISTERED ISO 9001 REGISTERED

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

LIST OF EFFECTIVE PAGES

The list of effective pages lists the status of all pages in this manual. Pages of the original issue are identified by a zero in the Change No. column. Pages subsequently changed are identified by the date of the change number. On a changed page, the text affected by the latest change is indicated by a vertical bar in the margin opposite the changed material.

Original Issue ........................................... 15 October 2004

Change 1 ...................................................15 January 2005

Total number of printed sides in this manual is 245 as listed below:

CHANGE CHANGE

PAGE # DATE PAGE # DATE

Title 0 15 January 2005 Title (Rear) - Blank Effective (1) 1 15 January 2005 Effective (2) 1 15 January 2005 Effective (3) 1 15 January 2005 Effective (4) - Blank Safety (1) 0 15 October 2004 Safety (2) 0 15 October 2004 Safety (3) 0 15 October 2004 Safety (4) 0 15 October 2004 Warranty (1) 0 15 October 2004 Warranty (2) 0 15 October 2004 Contents (1) 0 15 October 2004 Contents (2) 0 15 October 2004 Contents (3) 0 15 October 2004 Contents (4) 0 15 October 2004 Contents (5) 0 15 October 2004 Contents (6) 0 15 October 2004 Contents (7) 0 15 October 2004 Contents (8) 0 15 October 2004 Contents (9) 0 15 October 2004 Contents (10) 1 15 January 2005 1-1 0 15 October 2004 1-2 0 15 October 2004 1-3 0 15 October 2004 1-4 0 15 October 2004 1-5 0 15 October 2004 1-6 0 15 October 2004 1-7 1 15 January 2005 1-8 0 15 October 2004 2-1 1 15 January 2005 2-2 1 15 January 2005 2-3 0 15 October 2004 2-4 0 15 October 2004

2-5 1 15 January 2005 2-6 0 15 October 2004 2-7 0 15 October 2004 2-8 0 15 October 2004 2-9 0 15 October 2004 2-10 0 15 October 2004 2-11 1 15 January 2005 2-12 0 15 October 2004 2-13 0 15 October 2004 2-14 0 15 October 2004 2-15 1 15 January 2005 2-16 1 15 January 2005 2-17 0 15 October 2004 2-18 0 15 October 2004 3-1 0 15 October 2004 3-2 0 15 October 2004 3-3 0 15 October 2004 3-4 0 15 October 2004 3-5 0 15 October 2004 3-6 0 15 October 2004 3-7 1 15 January 2005 3-8 1 15 January 2005 3-9 0 15 October 2004 3-10 0 15 October 2004 3-11 0 15 October 2004 3-12 0 15 October 2004 3-13 0 15 October 2004 3-14 0 15 October 2004 3-15 0 15 October 2004 3-16 0 15 October 2004 4-1 0 15 October 2004 4-2 0 15 October 2004 4-3 1 15 January 2005 4-4 1 15 January 2005

Effective Pages (Page 1)

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LIST OF EFFECTIVE PAGES (Continued)

PAGE # DATE PAGE # DATE

CHANGE CHANGE

4-5 0 15 October 2004 4-6 0 15 October 2004 4-7 0 15 October 2004 4-8 0 15 October 2004 4-9 0 15 October 2004 4-10 0 15 October 2004 4-11 0 15 October 2004 4-12 0 15 October 2004 4-13 0 15 October 2004 4-14 0 15 October 2004 4-15 0 15 October 2004 4-16 0 15 October 2004 4-17 0 15 October 2004 4-18 0 15 October 2004 5-1 0 15 October 2004 5-2 0 15 October 2004 5-3 0 15 October 2004 5-4 1 15 January 2005 5-5 0 15 October 2004 5-6 0 15 October 2004 5-7 0 15 October 2004 5-8 0 15 October 2004 5-9 0 15 October 2004 5-10 0 15 October 2004 5-11 0 15 October 2004 5-12 0 15 October 2004 5-13 0 15 October 2004 5-14 0 15 October 2004 5-15 0 15 October 2004 5-16 0 15 October 2004 5-17 0 15 October 2004 5-18 0 15 October 2004 5-19 0 15 October 2004 5-20 0 15 October 2004 5-21 0 15 October 2004 5-22 0 15 October 2004 5-23 0 15 October 2004 5-24 0 15 October 2004 5-25 0 15 October 2004 5-26 0 15 October 2004 5-27 1 15 January 2005 5-28 1 15 January 2005 5-29 0 15 October 2004 5-30 0 15 October 2004 5-31 1 15 January 2005 5-32 - Blank 6-1 0 15 October 2004 6-2 0 15 October 2004

6-3 0 15 October 2004 6-4 0 15 October 2004 6-5 0 15 October 2004 6-6 0 15 October 2004 6-7 0 15 October 2004 6-8 0 15 October 2004 6-9 0 15 October 2004 6-10 0 15 October 2004 6-11 0 15 October 2004 6-12 0 15 October 2004 6-13 0 15 October 2004 6-14 - Blank 7-1 0 15 October 2004 7-2 0 15 October 2004 7-3 0 15 October 2004 7-4 0 15 October 2004 7-5 0 15 October 2004 7-6 0 15 October 2004 7-7 0 15 October 2004 7-8 0 15 October 2004 7-9 0 15 October 2004 7-10 0 15 October 2004 7-11 0 15 October 2004 7-12 0 15 October 2004 7-13 0 15 October 2004 7-14 0 15 October 2004 7-15 0 15 October 2004 7-16 0 15 October 2004 7-17 0 15 October 2004 7-18 0 15 October 2004 7-19 0 15 October 2004 7-20 0 15 October 2004 7-21 0 15 October 2004 7-22 0 15 October 2004 7-23 0 15 October 2004 7-24 0 15 October 2004 7-25 0 15 October 2004 7-26 0 15 October 2004 7-27 0 15 October 2004 7-28 0 15 October 2004 7-29 0 15 October 2004 7-30 0 15 October 2004 7-31 0 15 October 2004 7-32 0 15 October 2004 7-33 0 15 October 2004 7-34 0 15 October 2004 7-35 0 15 October 2004 7-36 0 15 October 2004

Effective Pages (Page 2)

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LIST OF EFFECTIVE PAGES (Continued)

PAGE No. DATE PAGE No. DATE

CHANGE CHANGE

7-37 0 15 October 2004 7-38 0 15 October 2004 7-39 0 15 October 2004 7-40 0 15 October 2004 7-41 0 15 October 2004 7-42 0 15 October 2004 8-1 0 15 October 2004 8-2 0 15 October 2004 8-3 0 15 October 2004 8-4 0 15 October 2004 8-5 0 15 October 2004 8-6 0 15 October 2004 8-7 0 15 October 2004 8-8 0 15 October 2004 8-9 0 15 October 2004 8-10 0 15 October 2004 8-11 0 15 October 2004 8-12 0 15 October 2004 8-13 0 15 October 2004 8-14 0 15 October 2004 8-15 0 15 October 2004 8-16 0 15 October 2004 8-17 0 15 October 2004 8-18 0 15 October 2004 8-19 0 15 October 2004 8-20 0 15 October 2004 8-21 0 15 October 2004 8-22 0 15 October 2004 9-1 0 15 October 2004 9-2 0 15 October 2004 9-3 0 15 October 2004 9-4 - Blank SD-1 0 15 October 2004 SD-2 0 15 October 2004 SD-3 0 15 October 2004 SD-4 0 15 October 2004 SD-5 0 15 October 2004 SD-6 0 15 October 2004 SD-7 0 15 October 2004 SD-8 0 15 October 2004 SD-9 0 15 October 2004 SD-10 0 15 October 2004 SD-11 0 15 October 2004 SD-12 0 15 October 2004

SD-13 0 15 October 2004 SD-14 0 15 October 2004 10-1 0 15 October 2004 10-2 0 15 October 2004 MD-1 0 15 October 2004 MD-2 0 15 October 2004 MD-3A 0 15 October 2004 MD-3B 0 15 October 2004 MD-4 0 15 October 2004 MD-5 0 15 October 2004 MD-6 0 15 October 2004 MD-7 0 15 October 2004 MD-8 0 15 October 2004 MD-9 0 15 October 2004 MD-10 0 15 October 2004 MD-11 0 15 October 2004 MD-12 0 15 October 2004 MD-13 0 15 October 2004 MD-14 0 15 October 2004 MD-15 0 15 October 2004 MD-16 0 15 October 2004 MD-17 0 15 October 2004 MD-18 0 15 October 2004 MD-19 0 15 October 2004 MD-20 0 15 October 2004 MD-21 0 01June 2004 MD-22 0 15 October 2004 MD-23 0 15 October 2004 MD-24 0 15 October 2004 MD-25 0 15 October 2004 MD-26 0 15 October 2004 MD-27 0 15 October 2004 MD-28 0 15 October 2004 MD-29 0 15 October 2004 MD-30 0 15 October 2004 MD-31 0 15 October 2004 MD-32 0 15 October 2004 MD-33 0 15 October 2004 MD-34 0 15 October 2004

MD-36 0 15 October 2004 MD-37 0 15 October 2004 MD-38 0 15 October 2004

MD-35 0 15 October 2004

Effective Pages (Page 3)

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ARTIFICIAL RESPIRATION (MOUTH-TO-MOUTH)

(a) START MOUTH-TO-MOUTH BREATHING

IMMEDIATELY. SECONDS COUNT. Do not wait to loosen clothing, warm the casualty, or apply stimulants.

(b) ASSESS RESPONSIVENESS OF CASUALTY. Do not jar

casualty or cause further physical injury (

HELP. Do not leave casualty unattended (

(d) CHECK CAROTID PULSE (

(e) LAY CASUALTY ON HIS/HER BACK and place any

available jacket or blanket under his/her shoulders.

(f) TILT THE HEAD BACK AND LIFT THE CHIN to open the

airway (

(g) PINCH CASUALTY’S NOSE AND EXHALE TWO SLOW

BREATHS INTO CASUALTY (

(h) REMOVE YOUR MOUTH and check for breathing

(i) CONTINUE GIVING ONE BREATH EVERY FIVE

SECONDS without interruption. If any air is retained in the

stomach after exhalation by casualty, press gently on stomach to expel air.

(j) IF CHEST DOES NOT RISE CHECK for obstruction in

casualty’s mouth: clear foreign material using your finger, tissues, etc. Use chin lift and recommence mouth-to-mouth breathing.

(k) WHILE MOUTH-TO-MOUTH BREATHING IS

CONTINUED have someone else:

(l) DON’T GIVE UP. Continue without interruption until the

casualty is revived, or until a doctor pronounces the casualty dead. Four hours or more may be required.

(m) DO NOT PROVIDE ANYTHING ORALLY while victim is

unconscious.

Figure 4)

(a) Loosen casualty’s clothing. (b) Keep the casualty warm.

Figure 3)

Figure 5)

Figure 1)

Figure 2)

(Figure

Safety (Page 1)

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GENERAL RULES FOR TREATMENT FOR BURNS, BLEEDING, AND SHOCK

1. After casualty has revived, treat for injuries and shock.

2. Reassure casualty.

3. Try to make him comfortable.

4. Keep him reasonably warm but do not apply heat.

5. If thirsty, liquids may be given but no alcohol (no liquids should be given in cases of severe burns).

6. Treat burns or wounds. Infection danger in treating burns or wounds is very great so ensure hands are clean and do not handle affected areas more than necessary.

7. Do not apply salves, grease, etc. to burns.

8. Do not remove burned clothing which adheres to the skin or break blisters.

9. Cover the burn with a dry sterile dressing, piece of sheeting, etc.

10. Bandage lightly over blisters where care must be taken to cover and not to break.

11. If severe bleeding of wound, elevate affected area, except in the case of a fracture.

12. Expose wound and apply pressure.

13. Apply dressing, pad and bandage.

14. For burns and bleeding, immobilize injured part using splints if necessary and keep patient in restful position during removal to hospital or expert medical attention.

15. In all cases, send for medical aid immediately.

Safety (Page 2)

15 October 2004

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

ELECTRIC SHOCK - RESCUE METHODS

Electricity can damage the body in a number of ways. It may interfere with the proper functioning of the nervous system and the heart action, it can subject the body to extreme heat and can cause severe muscular contractions. The path that the current of electricity takes through the body is important. Currents which pass from hand to hand or from hand to foot may pass directly through the heart and upset its normal functioning. This threat to life is related to the amount of current or amperage that will flow through a victim's body. Very little current (as little as 10 milliamps) can result in severe shock or death.

Speed in the application of first aid measures is absolutely essential in cases of electrical injury. As soon as the victim is freed safely from the source of the electrical current, if breathing has stopped, artificial respiration should be commenced immediately. If the carotid pulse cannot be felt, external cardiac massage should be commenced simultaneously. Resuscitation should be continued until the patient is breathing on his own or until medical aid arrives. Survival rates can be quite high if cardio-pulmonary resuscitation is started within 3 to 4 minutes of the injury being received.

ACT AT ONCE - DELAY OR INDECISION MAY BE FATAL

1. Turn OFF the electrical source.

2. Commence artificial respiration immediately.

3. Treat for burns, bleeding and shock.

REMOVING A CASUALTY FROM ELECTRICAL CONTACT

LOW VOLTAGE - 0 to 240 volts (household use)

Switch off the current, if possible and time permits. If the switch cannot be located immediately and the supply is through a flexible cord or cable, the current may be shut off by removing the plug or even breaking the cable or wrenching free. Never attempt to shut off current by cutting cord with a knife or scissors.

If the current cannot be shut off, the greatest care is necessary in removing the casualty. Household rubber gloves, rubber or plastic hose (if there is no water in them), a dry unpainted stick or a clean dry rope can be used to free victim.

HIGH VOLTAGE - 240 volts and up (industrial machines and power lines)

Do not touch any person or equipment in contact with a wire.

Use a dry unpainted pole, clean dry rope, dry rubber or plastic water hose to separate the casualty from the contact.

Keep as far away as possible.

Do not touch the casualty until he is free.

Safety (Page 3)

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TOXIC HAZARD WARNING

There are devices used in this equipment containing BERYLLIUM OXIDE ceramic, which is non-hazardous during normal device operation and under normal device failure conditions. These devices are specifically identified in the equipment manual’s parts list(s).

DO NOT cut, crush or grind devices because the resulting dust may be HAZARDOUS IF INHALED. Unserviceable devices should be disposed of as harmful waste.

Safety (Page 4)

15 October 2004

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

WARRANTY

Nautel Limited/Nautel Maine Incorporated, hereinafter referred to as Nautel, guarantees all mechanical and electrical parts of the equipment for a period of thirteen months from date of shipment.

1. A "Part Failure" shall be deemed to have occurred when the part has become defective, or does not have the

characteristics required for the specified equipment performance:

(a) When the equipment is operated within the design parameters, and

(b) When the equipment is installed and adjusted according to Nautel's prescribed procedures as stated in the

instruction manual.

2. Nautel shall provide replacements for all "Parts" at no cost to the Customer when they become defective during

the warranty period, and upon the return of the defective part.

3. In the event that a "Part" fails during the warranty period and causes damage to a sub-assembly that cannot be

readily repaired in the field, the entire sub-assembly so damaged may be returned to Nautel for repair. The repairs will be made without charge to the Customer.

4. Where warranty replacements or repair are provided under items 2 or 3, Nautel will pay that part of the

shipping costs incurred in returning the part/assembly to the Customer.

5. Warranty replacement parts and repair, which are provided under items 2 or 3, shall be guaranteed for a period

of ninety days from date of shipment or until the end of the original warranty period, whichever occurs later.

6. Nautel will not assume responsibility for any charges incurred by other than Nautel employees.

7. Nautel shall have the privilege of investigating whether failures have been caused by factors beyond its

control.

8. Nautel shall in no event be liable for any consequential damages arising from the use of this equipment.

9. When requesting a warranty repair/replacement, please provide complete and accurate information. Observe

the instructions regarding 'Equipment Being Returned to Nautel' on page two of this warranty and provide the information requested.

10. When ordering spare/replacement parts; please provide complete and accurate information. Refer to the parts

list of this manual for ordering information. Provide as much of the information requested for 'Equipment Being Returned to Nautel' on page two of this warranty as is practical. The information identified by an asterisk is the minimum required.

ON-LINE PART QUOTES

Nautel provides an on-line website service (www.nautel.com/in-service.html) where requests for part quotes may be submitted. Requests will normally be responded to within one working day.

Warranty (Page 1)

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500 WATT RADIOBEACON TRANSMITTER

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FACTORY SUPPORT

TECHNICAL ASSISTANCE

Nautel's field service department provides telephone technical assistance on a 24 hour, seven days a week basis. Requests by other media (facsimile or e-mail) will be responded to the next working day if received after Nautel's normal working hours. Contact the appropriate field service centre from the following:

U.S.A. customers use:

201 Target Industrial Circle Facsimile 207-947-3693 Bangor, Maine 04401

All other customers use: Nautel Limited Telephone 902-823-3900 (24 hours)

10089 Peggy’s Cove Road Facsimile 902-823-3183 Hackett’s Cove, NS, Canada E-Mail support@nautel.com B3Z 3J4 Web www.nautel.com

MODULE EXCHANGE SERVICE

In order to provide Nautel customers with a fast and efficient service in the event of a problem, Nautel operates a factory rebuilt, module exchange service which takes full advantage of the high degree of module redundancy in Nautel equipment. This module exchange service is operated from Nautel’s factory in Bangor, Maine and Hackett’s Cove, Nova Scotia. These two locations allow us to provide a quick turn around service to keep our customers on the air. During the transmitter’s warranty period, up to thirteen months from shipment, repair and exchange of modules is at no charge to the customer. When the warranty has expired, a charge of 80% of the list price for all exchanged modules is made. If the faulty module is returned to Nautel within 30 days, a credit is issued reducing this charge by one half to 40% of the list price. U.S.A. customers are required to contact our Bangor, Maine facility. Canadian and overseas customers should contact our Nova Scotia, Canada facility.

EQUIPMENT BEING RETURNED TO NAUTEL

All equipment being returned to Nautel and all requests for repairs or replacements should be marked 'field return' and addressed to the appropriate Nautel facility.

Complete and accurate information regarding the equipment being returned will ensure prompt attention and will expedite the dispatch of replacements. Refer to the nameplate on the transmitter and/or the appropriate module/assembly to obtain name, type, part and serial number information. Refer to the parts list of this manual or the appropriate service instruction manual for additional ordering information.

The following information should accompany each request:

* Model of Equipment * Serial number of Equipment * Name of Part/Assembly Serial number of Part/Assembly * Complete reference designation of Part/Assembly * Nautel's part number of Part/Assembly * OEM's part number of Part/Assembly Number of hours in Use Nature of defect * Return shipping address

* Denotes minimum information required to order spare/replacement parts

Nautel Maine Incorporated Telephone 207-947-8200 (24 hours)

Warranty (Page 2)

15 October 2004

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

TABLE OF CONTENTS

Section Page

1 GENERAL INFORMATION

1.1 INTRODUCTION................................................................................................................... 1-1

1.2 PURPOSE AND SCOPE OF MANUAL .............................................................................. 1-1

1.3 PURPOSE OF EQUIPMENT................................................................................................ 1-1

1.4 FACTORY REPAIR SERVICE............................................................................................. 1-1

1.5 MECHANICAL DESCRIPTION............................................................................................ 1-1

1.5.1 TRANSMITTER CHASSIS.................................................................................................... 1-1

1.6 DUPLICATED MODULES/ASSEMBLIES .......................................................................... 1-2

1.7 TECHNICAL SUMMARY ..................................................................................................... 1-2

1.8 SPECIAL TOOLS AND TEST EQUIPMENT....................................................................... 1-2

1.9 GLOSSARY OF TERMS ...................................................................................................... 1-2

2 THEORY OF OPERATION

2.1 GENERAL ............................................................................................................................. 2-1

2.2 TRANSMITTER DESCRIPTION .......................................................................................... 2-1

2.3 CONTROL/MONITOR PANEL............................................................................................. 2-1

2.3.1 LOCAL/REMOTE CONTROL ............................................................................................... 2-1

2.3.2 NORMAL\BYPASS CONTROL ............................................................................................ 2-1

2.3.3 RF CONTROL SWITCH ....................................................................................................... 2-1

2.3.4 ALARM LAMPS ..................................................................................................................... 2-2

2.3.4.1 Battery-Alarm Lamp........................................................................................................ 2-2

2.3.4.2 RF Current-Alarm Lamp.................................................................................................2-2

2.3.4.3 SWR-Alarm Lamp........................................................................................................... 2-2

2.3.4.4 Standby-Alarm Lamp...................................................................................................... 2-2

2.3.4.5 Shutdown-Alarm Lamp...................................................................................................2-2

2.3.5 SELECT MAIN TX SWITCHING .......................................................................................... 2-2

2.3.6 SWITCHED METERING....................................................................................................... 2-2

2.3.6.1 Test-Power/Mod Meter/Switch....................................................................................... 2-2

2.3.6.2 Test Volts/Current Meter/Test Switch ............................................................................ 2-2

2.4 MODULATOR/POWER AMPLIFIER MODULE.................................................................. 2-2

2.4.1 MODULATOR (A2A1) ........................................................................................................... 2-3

2.4.2 POWER AMPLIFIER (A2A2) ................................................................................................ 2-3

2.5 EXCITER MODULE .............................................................................................................. 2-4

2.5.1 +15 VDC REGULATOR ........................................................................................................2-4

2.5.2 -15 VDC REGULATOR ......................................................................................................... 2-4

2.5.3 KEYING/MOD SWITCH ........................................................................................................2-4

2.5.4 POWER TRIM ....................................................................................................................... 2-4

2.5.5 KEYER PWB (A4A1)............................................................................................................. 2-5

2.5.6 RF OSCILLATOR PWB (A4A3)............................................................................................ 2-6

2.5.6.1 Crystal Oscillator............................................................................................................. 2-6

2.5.6.2 External RF Drive Input .................................................................................................. 2-6

2.5.7 RF SYNTHESIZER PWB (A4A3) ......................................................................................... 2-6

2.5.8 RF DRIVE AMPLIFIER (A4A4)............................................................................................. 2-6

2.5.9 MODULATOR DRIVER PWB (A4A2) .................................................................................. 2-6

2.5.9.1 Voice Audio Filter............................................................................................................ 2-7

2.5.9.2 Voice Audio Amplifier/Limiter .........................................................................................2-7

2.5.9.3 Emission Mode Multiplexer ............................................................................................ 2-7

Contents (Page 1)

15 January 2005

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

TABLE OF CONTENTS (Continued)

Section Page

2 THEORY OF OPERATION

2.5.9.4 Line Volts Compensation/Power Trim Control .............................................................. 2-7

2.5.9.5 PWM Square-Wave Generator...................................................................................... 2-7

2.5.9.6 Ramp Integrator.............................................................................................................. 2-7

2.5.9.7 Linear Attenuator ............................................................................................................ 2-8

2.5.9.8 Variable Pulse-Width Generator .................................................................................... 2-8

2.5.9.10 Balanced Drive ............................................................................................................... 2-8

2.5.9.11 Pulse-Width Fault Detector ............................................................................................ 2-9

2.5.9.12 RF Drive Alarm Circuit.................................................................................................... 2-9

2.6 POWER ON/OFF PANEL ASSEMBLY ............................................................................... 2-9

2.7 POWER SUPPLY MODULES.............................................................................................. 2-9

2.7.1 POWER SUPPLY CONTROL PWB (A7A1) ........................................................................ 2-9

2.7.2 B- VDC To +24 VOLT DC CONVERTER PWB (A7A2) .................................................... 2-11

2.7.3 AC SUPPLY MONITOR (A7A3) ASSEMBLY .................................................................... 2-11

2.8 HARMONIC FILTER ASSEMBLY (A9)............................................................................. 2-11

2.8.1 RF CURRENT PROBE (A9A1) .......................................................................................... 2-11

2.8.2 FWD/REFL POWER PROBE (A9A2)................................................................................. 2-12

2.8.2.1 RF MON Switching....................................................................................................... 2-12

2.9 MONITOR PWB (A10)........................................................................................................ 2-12

2.9.1 TEST SWITCH CONTROL ................................................................................................. 2-12

2.9.2 RELAY SWITCHING ........................................................................................................... 2-12

2.9.2.1 Remote On/Off Relay ................................................................................................... 2-12

2.9.2.2 A/B Main Select ............................................................................................................ 2-13

2.9.2.3 Shutdown Relay............................................................................................................ 2-13

2.9.2.4 Standby Relay .............................................................................................................. 2-13

2.9.3 MONITOR +15 VOLT DC REGULATOR ........................................................................... 2-13

2.9.4 MONITOR -15 VOLTS DC CIRCUIT.................................................................................. 2-13

2.9.5 MOD THRESHOLD CIRCUIT ............................................................................................ 2-13

2.9.6 CARRIER THRESHOLD CIRCUIT .................................................................................... 2-14

2.9.7 CHANGEOVER DELAY CIRCUIT ..................................................................................... 2-14

2.9.8 STANDBY CIRCUIT............................................................................................................ 2-14

2.9.9 SHUTDOWN CIRCUIT ....................................................................................................... 2-14

2.9.10 FORWARD POWER CAL................................................................................................... 2-15

2.9.11 AUDIO MONITOR CIRCUIT............................................................................................... 2-15

2.9.11.1 Speaker Control............................................................................................................ 2-15

2.9.12 RF CURRENT CIRCUIT..................................................................................................... 2-15

2.9.13 SWR CUTBACK THRESHOLD CIRCUIT.......................................................................... 2-15

2.9.14 POWER TRIM INTERFACE CONTROL CIRCUIT............................................................ 2-16

2.9.15 REFLECTED POWER/REFL PWR CAL CIRCUIT ........................................................... 2-16

2.9.16 MOD% CONTROL CIRCUIT.............................................................................................. 2-16

2.9.17 AC POWER MONITOR CIRCUIT (DC Option Installed)................................................... 2-16

2.9.18 AC POWER MONITOR CIRCUIT (DC Option Not Installed) ............................................ 2-17

2.9.19 MONITOR BYPASS CIRCUIT............................................................................................ 2-17

2.10 BATTERY CONTROL PANEL (A11) ASSEMBLY........................................................... 2-17

2.10.1 BATTERY CONTROL PWB (A11A1)................................................................................. 2-17

2.10.1.1 Low Battery Voltage Monitor ........................................................................................ 2-18

(Continued)

Contents (Page 2)

15 January 2005

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

TABLE OF CONTENTS (Continued)

Section Page

3 INSTALLATION AND PREPARATION FOR USE

3.1 GENERAL ............................................................................................................................ 3-1

3.1.1 VISUAL INSPECTION .......................................................................................................... 3-1

3.2 TEST EQUIPMENT............................................................................................................... 3-1

3.3 SITE REQUIREMENTS ........................................................................................................ 3-1

3.3.1 LIGHTNING/SAFETY GROUND .......................................................................................... 3-1

3.3.2 ANTENNA SYSTEM ............................................................................................................. 3-1

3.3.3 ELECTRICAL POWER .........................................................................................................3-1

3.3.3.1 AC Power Requirements................................................................................................ 3-1

3.3.3.2 DC Power Requirements ............................................................................................... 3-1

3.3.4 ELECTRICAL POWER CABLING ........................................................................................ 3-2

3.3.5 RF FEED CABLE .................................................................................................................. 3-2

3.3.6 CONTROL/MONITOR CABLING ......................................................................................... 3-2

3.3.7 VENTILATION ...................................................................................................................... 3-2

3.3.8 HEATING ............................................................................................................................... 3-2

3.3.9 WORK AREA......................................................................................................................... 3-2

3.4 EXTERNAL INPUT/OUTPUT CIRCUIT REQUIREMENTS................................................ 3-2

3.4.1 EXTERNAL AUDIO SOURCE .............................................................................................. 3-2

3.4.2 REMOTE CONTROL CIRCUITS.......................................................................................... 3-2

3.4.2.1 Standby '1' and Standby '2' Controls ............................................................................. 3-2

3.4.2.2 Battery Reset Control ..................................................................................................... 3-2

3.4.2.3 Power Trim 'A' and 'B' Controls...................................................................................... 3-2

3.4.2.4 Remote Off Control......................................................................................................... 3-2

3.4.2.5 A/B Main Select Control ................................................................................................. 3-2

3.4.2.6 Press-To-Talk Control .................................................................................................... 3-3

3.4.3 EXTERNAL STATUS MONITORING................................................................................... 3-3

3.4.3.1 External Forward Power Monitoring............................................................................... 3-3

3.4.3.2 External Reflected Power Monitoring............................................................................. 3-3

3.4.3.3 External Modulation Percentage Monitoring.................................................................. 3-3

3.4.3.4 Audio Monitor.................................................................................................................. 3-3

3.4.3.5 Internal Standby Monitoring ...........................................................................................3-3

3.4.3.6 SWR Standby Monitoring............................................................................................... 3-3

3.4.4 EXTERNAL ALARM MONITORING CIRCUITS .................................................................. 3-3

3.4.4.1 Standby-Alarm ................................................................................................................ 3-3

3.4.4.2 Shutdown-Alarm ............................................................................................................. 3-3

3.4.4.3 SWR-Alarm..................................................................................................................... 3-3

3.4.4.4 Battery Alarm .................................................................................................................. 3-4

3.5 UNPACKING......................................................................................................................... 3-4

3.5.1 TRANSMITTER CABINET CRATE ...................................................................................... 3-4

3.5.2 POWER SUPPLY MODULE CRATE ................................................................................... 3-4

3.5.3 EXCITER AND MODULATOR/POWER AMPLIFIER MODULE CRATE ........................... 3-5

3.6 ANCILLARY PARTS ............................................................................................................3-5

3.7 USER ASSIGNED INFORMATION ..................................................................................... 3-5

3.7.1 CARRIER FREQUENCY ...................................................................................................... 3-5

3.7.2 TONE FREQUENCY............................................................................................................. 3-5

3.7.3 IDENTIFICATION CODE ......................................................................................................3-5

3.7.4 STANDBY CODES ............................................................................................................... 3-5

3.7.4.1 Standby 1 (A) Code ........................................................................................................ 3-5

3.7.4.2 Standby 2 (A) Code ........................................................................................................ 3-5

3.7.4.3 Standby 1 (B) Code ........................................................................................................ 3-5

3.7.4.4 Standby 2 (B) Code ........................................................................................................ 3-5

Contents (Page 3)

15 January 2005

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

TABLE OF CONTENTS (Continued)

Section Page

3 INSTALLATION AND PREPARATION FOR USE (Continued)

3.7.5 MEAN LEVEL OF AC POWER SOURCE............................................................................ 3-5

3.8 PARTS REQUIRED BUT NOT SUPPLIED......................................................................... 3-6

3.8.1 OSCILLATOR CRYSTALS ................................................................................................... 3-6

3.9 PRE-INSTALLATION PROCEDURES................................................................................ 3-6

3.9.1 DISASSEMBLY REQUIRED ................................................................................................ 3-6

3.9.2 EXCITER MODULE PRE-INSTALLATION .......................................................................... 3-6

3.9.2.1 RF Synthesizer PWB...................................................................................................... 3-6

3.9.2.2 RF Oscillator PWB.......................................................................................................... 3-6

3.9.3 KEYER PWB PRE-INSTALLATION..................................................................................... 3-7

3.9.3.1 Keyer Content Configuration.......................................................................................... 3-7

3.9.3.2 Keyed Tone Frequency ..................................................................................................3-8

3.9.3.3 Keyed Tone Source........................................................................................................ 3-8

3.9.3.4 Keyed Fault Inhibit.......................................................................................................... 3-8

3.9.4 POWER TRANSFORMERS A7T1 and A8T1 PRIMARY TAP SELECTION...................... 3-8

3.9.5 HARMONIC FILTER PRE-INSTALLATION ......................................................................... 3-9

3.10 INSTALLATION PROCEDURES....................................................................................... 3-11

3.10.1 TRANSMITTER MODULE INSTALLATION ...................................................................... 3-11

3.10.1.1 Power Supply Modules A7/A8...................................................................................... 3-11

3.10.1.2 Modulator/Power Amplifier Modules ............................................................................ 3-11

3.10.1.3 Exciter Modules ............................................................................................................ 3-11

3.10.2 EXTERNAL INPUT/OUTPUT INTERFACE CONNECTIONS........................................... 3-12

3.10.3 RF OUTPUT CABLE CONNECTION................................................................................. 3-12

3.10.4 LIGHTNING/SAFETY GROUND CONNECTION.............................................................. 3-12

3.10.5 AC AND DC POWER CONNECTION................................................................................ 3-12

3.11 FIRST STAGE (INITIAL START-UP)................................................................................. 3-13

3.12 SECOND STAGE (INITIAL START-UP) ........................................................................... 3-13

3.13 THIRD STAGE (INITIAL START-UP)................................................................................ 3-14

3.13.1 INTENDED CARRIER LEVEL............................................................................................ 3-14

3.13.2 RF MONITOR SIGNAL SOURCE SELECTION ................................................................ 3-14

3.13.3 INTENDED MODULATION DEPTH................................................................................... 3-14

4 OPERATING INSTRUCTIONS

4.1 GENERAL ............................................................................................................................ 4-1

4.2 EMERGENCY SHUTDOWN PROCEDURE ....................................................................... 4-1

4.3 CONTROLS AND INDICATORS ......................................................................................... 4-1

4.3.1 CONTROL/MONITOR PANEL CONTROLS AND INDICATORS....................................... 4-1

4.3.2 RF POWER MODULES CONTROLS AND INDICATORS ................................................. 4-1

4.3.3 EXCITER MODULE CONTROLS AND INDICATORS........................................................ 4-1

4.3.4 POWER ON/OFF PANEL CONTROLS AND INDICATORS .............................................. 4-1

4.3.5 POWER SUPPLY MODULE CONTROLS AND INDICATORS .......................................... 4-1

4.3.6 HARMONIC FILTER CONTROLS ....................................................................................... 4-1

4.3.7 MONITOR PWB CONTROLS AND INDICATORS.............................................................. 4-1

4.3.8 BATTERY PANEL CONTROLS AND INDICATORS .......................................................... 4-1

4.3.9 MISCELLANEOUS (CABINET/INTERFACE PANEL) CONTROLS AND INDICATORS .. 4-2

4.4 PRESTART-UP CHECKS .................................................................................................... 4-2

4.5 TURNING ON TRANSMITTER ............................................................................................ 4-2

4.6 RESETTING TRANSMITTER .............................................................................................. 4-2

4.7 MODULATION DEPTH WHEN USING A HIGH 'Q' ANTENNA ........................................ 4-2

4.7.1 RF CURRENT ALARM INDICATION................................................................................... 4-3

Contents (Page 4)

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500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

TABLE OF CONTENTS (Continued)

Section Page

4 OPERATING INSTRUCTIONS

4.7.2 SWR-ALARM INDICATION .................................................................................................. 4-3

4.7.3 REMEDIAL ACTION IN BEACON MODE............................................................................ 4-3

4.7.4 REMEDIAL ACTION IN VOICE AND BEACON MODE ...................................................... 4-3

4.8 MODULATION PERCENTAGE INDICATION .................................................................... 4-4

(Continued)

5 TESTING AND ADJUSTMENT

5.1 GENERAL ............................................................................................................................ 5-1

5.2 OPERATING OF EQUIPMENT............................................................................................ 5-1

5.3 TEST/ADJUSTMENT PROCEDURES ................................................................................ 5-1

5.3.1 TEST/ADJUSTMENT TEST EQUIPMENT .......................................................................... 5-2

5.3.2 TEST/ADJUSTMENT PREREQUISITES............................................................................. 5-2

5.3.3 TRANSMITTER TURN-ON................................................................................................... 5-2

5.3.4 DC VOLTAGE CHECKS....................................................................................................... 5-3

5.3.4.1 B- Voltage (No Load) Check .......................................................................................... 5-3

5.3.4.2 Logic/Control DC Voltage Checks ................................................................................. 5-3

5.3.5 CARRIER FREQUENCY CHECK ........................................................................................ 5-4

5.3.5.1 RF Synthesizer Check.................................................................................................... 5-4

5.3.5.2 RF Oscillator Check........................................................................................................ 5-4

5.3.6 RF DRIVE OUTPUT LEVEL CHECK ................................................................................... 5-5

5.3.7 PULSE WIDTH MODULATION DRIVE CHECK.................................................................. 5-5

5.3.8 RF CARRIER CHECK........................................................................................................... 5-6

5.3.9 MODULATION DEPTH (MCW) CHECK .............................................................................. 5-6

5.3.10 B- VOLTAGE (MCW) CHECK .............................................................................................. 5-7

5.3.11 AUDIO LIMITER BALANCE CHECK ................................................................................... 5-7

5.3.12 MODULATION DEPTH (A3E MODE) CHECK.................................................................... 5-8

5.3.13 IDENTIFICATION CODE CHECK ........................................................................................ 5-9

5.3.14 STANDBY '1' AND STANDBY '2' CODE CHECKS ............................................................. 5-9

5.3.15 FAULT THRESHOLDS/CHANGEOVER CHECK ............................................................. 5-10

5.3.15.1 Preliminary Changeover Procedures........................................................................... 5-10

5.3.15.2 Carrier Level Threshold Check .................................................................................... 5-10

5.3.15.3 Modulation Depth Fault Threshold Check ................................................................... 5-11

5.3.15.4 Changeover/Shutdown Check ..................................................................................... 5-12

5.3.16 SWR CUTBACK THRESHOLD CHECK............................................................................ 5-15

5.3.17 RF CURRENT THRESHOLD CHECK ............................................................................... 5-16

5.3.18 ALARM SYSTEMS CHECK................................................................................................ 5-16

5.3.18.1 RF Current-Alarm Check.............................................................................................. 5-17

5.3.18.2 SWR-Alarm Check ....................................................................................................... 5-17

5.3.18.3 Shutdown-Alarm Check................................................................................................ 5-17

5.3.18.4 Standby-Alarm Check .................................................................................................. 5-17

5.3.18.5 Battery-Alarm Check .................................................................................................... 5-17

5.3.18.6 Mod Drive-Alarm Check ............................................................................................... 5-17

5.3.18.7 RF Drive-Alarm Check ................................................................................................. 5-18

5.3.19 LOW AC POWER CHECK ................................................................................................. 5-18

5.3.20 LOW BATTERY VOLTAGE MONITOR ............................................................................. 5-18

5.3.21 TEST/ADJUSTMENT OF SIDE B ...................................................................................... 5-19

5.4 SPECIAL ADJUSTMENT PROCEDURES ....................................................................... 5-19

5.4.1 CURRENT SHUNT RESISTOR ADJUSTMENT ............................................................... 5-19

5.4.2 TEST METER ADJUSTMENT............................................................................................ 5-20

5.4.2.1 Forward Power Reading .............................................................................................. 5-20

Contents (Page 5)

15 January 2005

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

TABLE OF CONTENTS (Continued)

Section Page

5 TESTING AND ADJUSTMENT (Continued)

5.4.2.2 Reflected Power Reading ............................................................................................ 5-21

5.4.3 LOW AC VOLTAGE THRESHOLD ADJUSTMENT .......................................................... 5-21

5.4.4 LOW BATTERY VOLTAGE THRESHOLD ADJUSTMENT (DC OPTION INSTALLED). 5-22

5.4.4.1 Low Battery Voltage Threshold Adjustment Pre-requisites......................................... 5-22

5.4.4.2 Determination of Low Voltage Battery Threshold........................................................ 5-23

5.4.4.3 Finalization of Low Battery Voltage Threshold Adjustment......................................... 5-23

5.5 OPERATIONAL ADJUSTMENT PROCEDURES ............................................................ 5-24

5.5.1 OPERATIONAL ADJUSTMENT TEST EQUIPMENT ....................................................... 5-24

5.5.2 OPERATIONAL ADJUSTMENT PRE-REQUISITES ........................................................ 5-25

5.5.3 TRANSMITTER TURN-ON................................................................................................. 5-25

5.5.4 CARRIER LEVEL ADJUSTMENT ...................................................................................... 5-25

5.5.5 MODULATION DEPTH ADJUSTMENT............................................................................. 5-25

5.6 POST OPERATIONAL ADJUSTMENT PROCEDURES ................................................. 5-26

6 MAINTENANCE

6.1 GENERAL ............................................................................................................................ 6-1

6.2 ELECTRICAL SCHEMATICS/LOGIC DIAGRAMS ............................................................ 6-1

6.2.1 COMPONENT VALUES ....................................................................................................... 6-1

6.2.2 GRAPHIC SYMBOLS ........................................................................................................... 6-1

6.2.3 LOGIC SYMBOLS................................................................................................................. 6-1

6.2.4 REFERENCE DESIGNATIONS ........................................................................................... 6-1

6.3 WIRING INFORMATION ...................................................................................................... 6-1

6.3.1 TRANSMITTER CABINET WIRING ..................................................................................... 6-1

6.3.2 CONTROL/MONITOR PANEL WIRING .............................................................................. 6-1

6.3.3 MODULATOR/POWER AMPLIFIER MODULE WIRING .................................................... 6-1

6.3.4 EXCITER MODULE WIRING ............................................................................................... 6-1

6.3.5 POWER ON/OFF PANEL WIRING ...................................................................................... 6-1

6.3.6 POWER SUPPLY MODULE WIRING.................................................................................. 6-1

6.3.7 B- VDC TO +24 VDC CONVERTER WIRING ..................................................................... 6-1

6.3.8 HARMONIC FILTER ASSEMBLY WIRING ......................................................................... 6-1

6.3.9 FWD/REFL POWER PROBE WIRING ................................................................................ 6-1

6.3.10 BATTERY CONTROL PANEL WIRING............................................................................... 6-2

6.3.11 INTERFACE PANEL ASSEMBLY WIRING ......................................................................... 6-2

6.4 MECHANICAL DRAWINGS ................................................................................................ 6-2

6.5 SCHEDULED MAINTENANCE............................................................................................ 6-2

6.6 CORRECTIVE MAINTENANCE .......................................................................................... 6-2

6.7 ISOLATION OF DEFECTIVE POWER MOSFETS ............................................................. 6-2

6.7.1 ISOLATION OF DEFECTIVE POWER MOSFETs IN A POWER AMPLIFIER .................. 6-2

6.7.2 CHECK OF POWER MOSFET IN MODULATOR ASSEMBLY.......................................... 6-3

6.7.3 ISOLATION OF DEFECTIVE POWER MOSFETs IN RF DRIVE AMPLIFIER ASSY ....... 6-4

6.7.4 CHECK OF POWER MOSFET IN DC-DC CONVERTER ASSEMBLY ............................. 6-5

6.8 POWER MOSFET REPLACEMENT ................................................................................... 6-6

6.8.1 POWER MOSFET REPLACEMENT ON POWER AMPLIFIER ASSEMBLIES................. 6-6

6.8.2 POWER MOSFET REPLACEMENT ON MODULATOR ASSEMBLIES............................ 6-7

6.8.3 POWER MOSFET REPLACEMENT ON RF DRIVE AMPLIFIER ASSEMBLIES.............. 6-8

6.8.4 POWER MOSFET REPLACEMENT ON DC-DC CONVERTER ASSEMBLIES ............... 6-8

Contents (Page 6)

15 January 2005

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

TABLE OF CONTENTS (Continued)

Section Page

7 PARTS LIST

7.1 INTRODUCTION................................................................................................................... 7-1

7.2 FAMILY TREE ...................................................................................................................... 7-1

7.3 MANUFACTURER'S INDEX................................................................................................ 7-1

7.4 HOW TO LOCATE INFORMATION FOR A SPECIFIC PART ......................................... 7-1

7.4.1 WHEN NAUTEL CONFIGURATION CONTROL NUMBER IS KNOWN............................ 7-1

7.4.2 WHEN REF DES IS KNOWN .............................................................................................. 7-1

7.5 REFERENCE DESIGNATION INDEXES ........................................................................... 7-1

7.6 COLUMN CONTENT EXPLANATION ................................................................................ 7-1

7.6.1 USE CODE COLUMN .......................................................................................................... 7-1

7.6.2 REF DES COLUMN ............................................................................................................. 7-2

7.6.3 NAME OF PART AND DESCRIPTION COLUMN............................................................... 7-2

7.6.4 NAUTEL'S PART NO. COLUMN ......................................................................................... 7-2

7.6.5 JAN/MIL/OEM PART NO. COLUMN .................................................................................... 7-2

7.6.6 X/Y GRID COLUMN .............................................................................................................. 7-2

7.6.7 OEM CODE COLUMN ..........................................................................................................7-2

8 WIRING INFORMATION

8.1 INTRODUCTION................................................................................................................... 8-1

8.2 WIRING LISTS NOT PROVIDED ........................................................................................ 8-1

8.3 PRINTED WIRING PATTERNS .......................................................................................... 8-1

8.4 WIRE COLORS .................................................................................................................... 8-1

8.5 WIRING LISTS PROVIDED ................................................................................................. 8-1

9 ELECTRICAL SCHEMATICS

9.1 INTRODUCTION................................................................................................................... 9-1

9.2 COMPONENT VALUES. ..................................................................................................... 9-1

9.3 GRAPHIC SYMBOLS .......................................................................................................... 9-1

9.4 LOGIC SYMBOLS ............................................................................................................... 9-1

9.5 REFERENCE DESIGNATIONS ........................................................................................... 9-1

9.6 UNIQUE SYMBOLOGY........................................................................................................ 9-1

9.6.1 TYPE OF INPUTS/OUTPUTS .............................................................................................. 9-1

9.6.2 LOGIC LEVEL/CONVENTION ............................................................................................. 9-1

9.7 IDENTIFICATION OF SCHEMATIC DIAGRAMS............................................................... 9-1

9.8 STRUCTURE OF SCHEMATICS ........................................................................................ 9-1

9.9 LOCATING THE SCHEMATIC DIAGRAM(S) FOR A FUNCTIONAL BLOCK ................ 9-2

9.9.1 WHEN FIGURE NUMBER IDENTIFIED .............................................................................. 9-2

9.9.2 WHEN REFERENCE DESIGNATION ASSIGNED TO BLOCK ......................................... 9-2

9.9.3 TITLE OF BLOCK ................................................................................................................. 9-2

9.10 LOCATING A PART/ASSEMBLY IDENTIFIED ON A SCHEMATIC ................................ 9-2

10 MECHANICAL DRAWINGS

10.1 INTRODUCTION................................................................................................................. 10-1

10.2 LOCATING ASSEMBLY DETAIL DRAWINGS................................................................ 10-1

10.3 CONTENT OF MECHANICAL DRAWINGS ..................................................................... 10-1

10.4 X/Y CO-ORDINATES ON PWB DRAWINGS ................................................................... 10-1

Contents (Page 7)

15 January 2005

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

LIST OF ILLUSTRATIONS

Number Title Page

1-1 ND2000A Radiobeacon Transmitter .......................................................................................................... 1-3

1-2 Nautel's Identification .................................................................................................................................. 1-6

3-1 Positioning of Selector Plates E1 and E2 ................................................................................................. 3-10

3-2 External Input/Output Interface................................................................................................................. 3-16

6-1 Carrier Oscillator Frequency - CW ........................................................................................................... 6-10

6-2 Balanced Drive Output - CW .................................................................................................................... 6-10

6-3 Carrier Oscillator - CW.............................................................................................................................. 6-10

6-4 Balanced Drive Output - CW .................................................................................................................... 6-10

6-5 RF Drive Output (B- = 50 Vdc).................................................................................................................. 6-11

6-6 Not Used.................................................................................................................................................... 6-11

6-7 Tone Oscillator - CW................................................................................................................................. 6-11

6-8 Audio/Keyed Tone - MCW ........................................................................................................................ 6-11

6-9 PWM Ramp Integrator Output - CW......................................................................................................... 6-12

6-10 Mod Drive (PWM Output) - CW ................................................................................................................ 6-12

6-11 Mod Drive Alarm Condition ....................................................................................................................... 6-12

6-12 FWD Power Sample - MCW..................................................................................................................... 6-12

6-13 RF Current Status (RF Current lamp on) ................................................................................................. 6-13

6-14 RF Monitor................................................................................................................................................. 6-13

6-15 RF Monitor................................................................................................................................................. 6-13

7-1 Family Tree - ND2000A 500 Watt Radiobeacon Transmitter.................................................................... 7-6

SD-1 Electrical Schematic - ND2000A 500W Radiobeacon Transmitter (Sheet 1 of 2)................................. SD-1

SD-2 Electrical Schematic - ND2000A 500W Radiobeacon Transmitter (Sheet 2 of 2)................................. SD-2

SD-3 Electrical Schematic – NAC111/02 Control/Monitor Panel.....................................................................SD-3

SD-4 Electrical Schematic - NAP13B/02 Modulator/Power Amplifier Module................................................. SD-4

SD-5 Electrical Schematic - NAE45G Exciter Module ..................................................................................... SD-5

SD-6 Electrical Schematic – NAPE72 Keyer PWB .......................................................................................... SD-6

SD-7 Electrical Schematic - NAPE29C/02 Modulator Driver PWB (Sheet 1 of 2) .......................................... SD-7

SD-8 Electrical Schematic - NAPE29C/02 Modulator Driver PWB (Sheet 2 of 2) .......................................... SD-8

SD-9 Electrical Schematic - NAPE64A RF Oscillator (Optional DGPS Input) PWB ....................................... SD-9

SD-10 Electrical Schematic - NAS25B/03 & /04 Power Supply Module (NAPC26C/02 Control PWB) ......... SD-10

SD-11 Electrical Schematic - NAF46C/02 Harmonic Filter .............................................................................. SD-11

SD-12 Electrical Schematic - NAPC120/02 & NAPC120/04 Monitor PWB (Sheet 1 of 2).............................. SD-12

SD-13 Electrical Schematic - NAPC120/02 & NAPC120/04 Monitor PWB(Sheet 2 of 2)............................... SD-13

SD-14 Electrical Schematic - NAX50B/02 Battery Control Panel .................................................................... SD-14

MD-1 Assembly Detail - ND2000A 500W Radiobeacon Transmitter ..............................................................MD-1

MD-2 Assembly Detail – NAC111/02 Control/Monitor Panel (Front View) .....................................................MD-2

MD-3A Assembly Detail – NAC111/02 Control/Monitor Panel (Rear View) .................................................... MD-3A

MD-3B Assembly Detail - NAPD09/02 Display PWB ....................................................................................... MD-3B

MD-4 Assembly Detail - NAP13B/02 Modulator/Power Amplifier Module (Front View) ..................................MD-4

MD-5 Assembly Detail - NAP13B/02 Modulator/Power Amplifier Module (Top View).....................................MD-5

MD-6 Assembly Detail - NAP13B/02 Modulator/Power Amplifier Module (Left Side View) ............................MD-6

MD-7 Assembly Detail - NAP13B/02 Modulator/Power Amplifier Module (Right Side View)..........................MD-7

MD-8 Assembly Detail - NAP13B/02 Modulator/Power Amplifier Module (Bottom View) ...............................MD-8

MD-9 Assembly Detail - NAP13B/02 Modulator/Power Amplifier Module (Rear View)...................................MD-9

MD-10 Assembly Detail - NASM06/01 Modulator Assembly ............................................................................MD-10

MD-11 Assembly Detail - NAA02/02 Power Amplifier.......................................................................................MD-11

MD-12 Assembly Detail - Display Interface PWB (P/N 156-1037-01)..............................................................MD-12

MD-13 Assembly Detail - NAE45G Exciter Module (Front View) .....................................................................MD-13

MD-14 Assembly Detail - NAE45G Exciter Module (Left Side View) ...............................................................MD-14

Contents (Page 8)

15 January 2005

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

LIST OF ILLUSTRATIONS (Continued)

Number Title Page

MD-15 Assembly Detail - NAE45G Exciter Module (Right Side View).............................................................MD-15

MD-16 Assembly Detail - NAE45G Exciter Module (Rear View)......................................................................MD-16

MD-17 Assembly Detail - NAPE72 Keyer PWB................................................................................................MD-17

MD-18 Assembly Detail - NAPE29C/02 Modulator Driver PWB ......................................................................MD-18

MD-19 Assembly Detail - NAPE64A RF Oscillator PWB (Optional DGPS Input) ............................................MD-19

MD-20 Not used

MD-21 Assembly Detail - NAA21A/02 RF Drive Amplifier ................................................................................MD-21

MD-22 Assembly Detail - Power On/Off Panel (P/N 192-8130) .......................................................................MD-22

MD-23 Assembly Detail - NAS25B/03 & NAS25B/04 Power Supply Module (Front View) .............................MD-23

MD-24 Assembly Detail - NAS25B/03 & NAS25B/04 Power Supply Module (Top View) ...............................MD-24

MD-25 Assembly Detail - NAS25B/03 & NAS25B/04 Power Supply Module (Rear View) .............................MD-25

MD-26 Assembly Detail - NAPC26C/02 Power Supply Control PWB..............................................................MD-26

MD-27 Assembly Detail - NASC01/04 B- VDC To +24 VDC Converter ..........................................................MD-27

MD-28 Assembly Detail - NAPC32A/01 & NAPC32A/02 AC Supply Monitor PWB ........................................MD-28

MD-29 Assembly Detail - Interface Panel (P/N 192-8110) ...............................................................................MD-29

MD-30 Assembly Detail - NAF46C/02 Harmonic Filter (Front View) ................................................................MD-30

MD-31 Assembly Detail - NAF46C/02 Harmonic Filter (Rear View) ................................................................MD-31

MD-32 Assembly Detail - NAFP23/02 RF Current Probe .................................................................................MD-32

MD-33 Assembly Detail - NAFP24A/02 Forward/Reflected Power Probe .......................................................MD-33

MD-34 Assembly Detail - NAPC120/02 Monitor PWB ......................................................................................MD-34

MD-35 Assembly Detail - NAPC120/04 Monitor PWB ......................................................................................MD-35

MD-36 Assembly Detail - NAX50B/02 Battery Control Panel ...........................................................................MD-36

MD-37 Assembly Detail - Battery Controller PWB (P/N 156-7164-01) ............................................................MD-37

MD-38 Assembly Detail - ND2000A Radiobeacon Transmitter ........................................................................MD-38

LIST OF TABLES

Number Title Page

1-1 Duplicated Modules/Assemblies................................................................................................................. 1-2

1-2 Technical Summary .................................................................................................................................... 1-4

1-3 Test Equipment ........................................................................................................................................... 1-7

1-4 Glossary of Terms....................................................................................................................................... 1-8

3-1 Crystal Operating Frequencies................................................................................................................... 3-6

3-2 Selecting Primary Winding Taps of Power Transformer A7T1/A8T1 ........................................................ 3-8

3-3 Selecting Frequency Bank Links on Harmonic Filter A12 ........................................................................ 3-9

4-1 Preliminary Switch Settings ....................................................................................................................... 4-4

4-2 Control/Monitor Panel Controls and Indicators .......................................................................................... 4-5

4-3 Modulator/Power Amplifier Module Controls and Indicators...................................................................... 4-7

4-4 Exciter Module Controls and Indicators...................................................................................................... 4-8

4-5 Power On/Off Panel Controls and Indicators ........................................................................................... 4-12

4-6 Power Supply Module Controls and Indicators ........................................................................................ 4-13

4-7 Harmonic Filter Assembly Controls and Indicators .................................................................................. 4-14

4-8 Monitor/PWB Panel Controls and Indicators ............................................................................................ 4-15

4-9 Battery Panel Controls and Indicators ...................................................................................................... 4-17

4-10 Miscellaneous (Cabinet/Interface Panel) Controls and Indicators........................................................... 4-18

5-1 dB to Power/Voltage Conversion.............................................................................................................. 5-13

Contents (Page 9)

15 January 2005

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

LIST OF TABLES (Continued)

Number Title Page

5-2 Functional Test/Adjustment Check List .................................................................................................... 5-27

5-3 Morse Code Characters............................................................................................................................ 5-31

7-1 Manufacturers' Code to Address Index ..................................................................................................... 7-3

7-2 Ref Des Index - ND2000A-02x-xx0 (500 Watt) Radiobeacon Transmitter ............................................... 7-7

7-3 Ref Des Index – NAC111/02 Control/Monitor Panel.................................................................................. 7-9

7-4 Ref Des Index - NAPD09/02 Display PWB .............................................................................................. 7-10

7-5 Ref Des Index - NAP13B/02 Modulator/Power Amplifier Module............................................................ 7-11

7-6 Ref Des Index - NASM06/01 Modulator Assembly .................................................................................. 7-13

7-7 Ref Des Index - NAA02/02 Power Amplifier............................................................................................. 7-14

7-8 Ref Des Index - NAE45G/02 and /04 Exciter Module.............................................................................. 7-15

7-9 Ref Des Index – NAPE72 Keyer PWB .................................................................................................... 7-16

7-10 Ref Des Index - NAPE29C/02 Modulator Driver PWB............................................................................. 7-19

7-11 Ref Des Index - NAPE64A RF Oscillator PWB ....................................................................................... 7-23

7-12 Ref Des Index - NAA21A/02 RF Drive Amplifier ...................................................................................... 7-26

7-13 Ref Des Index - NAS25B/03 and NAS25B/04 Power Supply Module .................................................... 7-27

7-14 Ref Des Index - NAPC26C/02 Power Supply Control PWB.................................................................... 7-27

7-15 Ref Des Index - NASC01/04 B- VDC to +24 VDC Converter ................................................................. 7-30

7-16 Ref Des Index - NAPC32A/01 and NAPC32A/02 AC Supply Monitor PWB........................................... 7-31

7-17 Ref Des Index - NAF46C/02 Harmonic Filter ........................................................................................... 7-32

7-18 Ref Des Index – NAFP23/02 RF Current Probe ...................................................................................... 7-33

7-19 Ref Des Index - NAFP24A/02 Forward/Reflected Power Probe ............................................................. 7-34

7-20 Ref Des Index - NAPC120/02 and NAPC120/04 Monitor PWB .............................................................. 7-35

7-21 Ref Des Index - NAX50B/02 Battery Control Panel ................................................................................. 7-42

8-1 Wiring Lists Provided ................................................................................................................................. 8-1

8-2 Wiring List - ND2000A Transmitter Cabinet ............................................................................................... 8-2

8-3 Wiring List – NAC111/02 Control/Monitor Panel ........................................................................................ 8-7

8-4 Wiring List - NAP13B/02 Modulator/Power Amplifier Module....................................................................8-8

8-5 Wiring List - NAE45G/02 and /04 Exciter Module .................................................................................... 8-10

8-6 Wiring List - Power On/Off Panel (192-8130)........................................................................................... 8-12

8-7 Wiring List - NAS25B/03 and NAS25B/04 Power Supply Modules......................................................... 8-13

8-8 Wiring List - NASC01/04 B- VDC to +24 VDC Converter ........................................................................ 8-15

8-9 Wiring List - NAF46C/02 Harmonic Filter ................................................................................................. 8-16

8-10 Wiring List - NAFP24A/02 Forward/Reflected Power Probe .................................................................. 8-17

8-11 Wiring List - NAX50B/02 Battery Control Panel ....................................................................................... 8-18

8-12 Wiring List - Interface Panel Assembly (192-8110).................................................................................. 8-20

8-13 Connector Mating Information - Sorted By Floating Connector............................................................... 8-21

9-1 List of Electrical Schematics/Logic Diagrams ............................................................................................ 9-3

10-1 List of Mechanical Drawings ..................................................................................................................... 10-2

Contents (Page 10)

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SECTION 1

GENERAL INFORMATION

INTRODUCTION

1.1 The ND2000A radiobeacon transmitter is a

dual transmitter that operates in the LF/MF band at 500 watts maximum (carrier) power. It transmits beacon identification signals at a repetition rate of eight seconds. Provision is made for standby codes to be transmitted when the primary exciter/keyer is switched to the secondary exciter/keyer or when commanded from an external source. Provision is also made for press-to-talk voice telephony. Tone identification and voice signals utilize amplitude modulation. Refer to table 1-2 for a technical summary.

PURPOSE AND SCOPE OF MANUAL

1.2 This manual provides the information

necessary to install, operate and maintain the subject transmitter.

PURPOSE OF EQUIPMENT

1.3 When combined with an appropriate

antenna system, the transmitter provides reliable facilities for airfield locator or aeronautical enroute requirements. It is ideally suited for remote or unmanned sites. To determine the configuration of a specific transmitter, obtain the complete part number from the transmitter's nameplate and then refer to figure 1-2.

FACTORY REPAIR SERVICE

1.4 Nautel provides a factory module repair

service for users of Nautel's transmitters. Users who do not have repair facilities or who are not able to repair an assembly may utilize this service for a nominal fee. Refer to Warranty (page 2) for address of Nautel's repair facility and information to be supplied with returned parts.

MECHANICAL DESCRIPTION

1.5 The ND2000A radiobeacon transmitter is

packaged in a single cabinet that weighs approximately 400 pounds (182 kilograms). Refer to figure MD-38 for dimensional information. The RF output coaxial cable connects to a connector on the top of the transmitter cabinet. External ac power and, if applicable, dc power cabling enter the cabinet through cable entry holes on the lower, left and right rear section of the cabinet. External input (audio and control) and output (status and alarm monitoring) cabling enter the cabinet through cable entry holes on the top section of transmitter cabinet.

1.5.1 TRANSMITTER CHASSIS (see figures MD-1 through MD-38): The subject transmitter chassis is a fabricated metal cabinet that accepts standard 19-inch rack mounted assemblies. The rear section of the transmitter is fitted with a lockable, fulldepth hinged door. The cabinet is effectively divided into functional sections and the assemblies that are not plug-in or removable modules are fastened to support brackets. Side panels are removable to permit access to the interior during maintenance routines.

1.5.1.1 The cabinet contains the electrical components that are not installed in the plug-in modules and the mechanical positioning hardware to guide and align the plug-in modules. The connectors and the supporting hardware for the plug-in modules are integral parts of the cable wiring harness. Refer to figure MD-1 to determine the identity and location of the plug-in modules that form the subject transmitter. The control/monitor panel (A1) is mounted on a hinged door at the top, front section of the transmitter. Harmonic filter assembly (A9), monitor PWB (A10) and an optional battery panel (A11) are located immediately behind it. Access to these assemblies can be attained by opening the control/monitor panel's hinged door.

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Table 1-1 Duplicated Modules/Assemblies

NOMENCLATURE DESCRIPTION DESIGNATION QTY

NAUTEL REFERENCE

NAP13B/02 Modulator/Power Amplifier A2 and A3 2 NAE45G/02 or 04 Exciter A4 and A5 2 NAS25B/03 or NAS25B/04 Power Supply A7 and A8 2

1.5.1.2 Modulator/power amplifier modules (A2/ A3) are located below control monitor panel (A1). Exciter modules (A4/A5) are located directly below modulator/power amplifier modules (A2/A3). The power on/off panel (A6) is located directly below exciter modules (A4/A5). Power supply modules (A7/A8) are located at the bottom of the transmitter cabinet. All electrical connections to plug-in modules are made to connectors on the rear sections of the associated modules.

DUPLICATED MODULES/ASSEMBLIES

1.6 Table 1-1 lists the modules/assemblies

which are duplicated to effectively form a dual transmitter. They are easily removed to accommodate

TECHNICAL SUMMARY

1.7 Table 1-2 contains a detailed technical

summary for the transmitter.

TEST EQUIPMENT AND SPECIAL TOOLS

1.8 Table 1-3 lists the test equipment and

special tools required to operate and maintain the transmitter.

GLOSSARY OF TERMS

1.9 Table 1-4 provides a list of all unique

terms, abbreviations and acronyms used in this publication.

maintenance.

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500 WATT RADIOBEACON TRANSMITTER

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Figure 1-1 ND2000A Radiobeacon Transmitter

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Table 1-2 Technical Summary

Equipment Name............................................................................................................ LF/MF Radiobeacon Transmitter

Equipment Type Number .....................................................................................................................................ND2000A

Frequency Range........................................................................................................................................190 to 535 kHz

Frequency Control

Standard........................................................................................................................................ RF Synthesizer

Optional ....................................................................................................................Crystal Controlled Oscillator

Frequency Tolerance ........................................................ ± 0.0003% (RF synthesizer) Over Full Environmental Range

± 0.005% (crystal oscillator) Over Full Environmental Range

Type of Emission

NON ...............................................................................................................................(CW) Continuous Carrier

A2A.........................................................................................................................................(MCW) Keyed Tone

A2A and A3E ...................................................................................... (MCW) Simultaneous Telephony/Beacon

RF Carrier Output (one preset level)

AC Power Source ...................................................................... 100 Watts (Minimum) to 500 Watts (Maximum)

DC Power Source...................................................................... 100 Watts (Minimum) to 500 Watts (Maximum)

Peak Envelope Power ....................................................................................................Maximum of 2000 Watts

Keyed Tone Frequency.................................................................................................................. 400 or 1020 Hz (± 5%)

Modulation Level .............................................................................................................................. 0 to 95% (Adjustable)

Harmonics ..............................................................................................Not exceeding -80 dBs Relative to Carrier when

................................................................................................... Operating with Associated Antenna Tuning Unit

Level of Spurious Emissions (complies with)

Canada........................................................................................................... Radio Standards Specification 117

USA......................................................................................................................FCC Rules and Regulations 87

ICAO........................................................................................................................................................Annex 10

Audio Distortion .................................................................................................... Less than 4% at up to 95% Modulation

Audio Response ............................................................................................................. ±2 dB from 300 to 3000Hz (A3E)

Noise and Hum Level............................................. Not exceeding -46 dB Relative to 1020Hz at 95% Modulation Level

External Audio Input Level .........................................................................-20 to +20 dBm Across 600 ohms (Balanced)

Power Requirements (as ordered by user)

Voltage ...................................................................................................................................180 to 250 Volts AC

Frequency .............................................................................................................................................50 or 60Hz

Power ...................................................................................................................................... 1200 VA maximum

External Battery (optional) .................................................................................................................-48 Volts DC

Environmental Limits

Temperature ....................................................................................................................................-10°C to 55°C

Relative Humidity ..................................................................................................................................... 0 to 95%

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Table 1-2 Technical Summary (Continued)

Weight (unpacked) ........................................................................................ Approximately 257 kilograms (565 pounds)

Dimensions

Height........................................................................................................................ 165 centimetres (65 inches)

Width ........................................................................................................................... 61 centimetres (24 inches)

Depth........................................................................................................................... 61 centimetres (24 inches)

Airflow ....................................................................................................................... Approximately 90 cubic feet/minute

Heat Flushing (Maximum).........................................................................................................................1000 BTUs/hour

REMOTE MAINTENANCE MONITORING INPUTS/OUTPUTS

(1) ...................................................................................................................................................Forward Power

(2) .................................................................................................................................................Reflected Power

(3) ......................................................................................................................................Modulation Percentage

(4) .........................................................................................................................Power Trim (A) and (B) Control

(5) ....................................................................................................................................................... +24 Volts dc

(6) ....................................................................................................................................................... +15 Volts dc

(7) ..................................................................................................................................................B- (A or B Side)

External Controls

(1) ..................................................................................................................... Remote System ON/OFF Control

(2) ............................................................................................................................ Voice (Press-to-Talk) Control

(3) ......................................................................................................................... Remote Standby Code Control

(4) ........................................................................................................................ 600 Ohm Balanced Audio Input

(5) ......................................................................................................................................................Standby Test

(6) ..................................................................................................................................................... Battery Reset

External Alarms/Status Outputs:

(1) .............................................................................................................................................Changeover Alarm

(2) ................................................................................................................................................ Shutdown Alarm

(3) ........................................................................................................................................................ SWR Alarm

(4) ..................................................................................................................................................... Battery Alarm

(5) .......................................................................................................................................Remote Audio Monitor

Transmitter Failure Threshold................................................................................. Changeover to Standby Will Occur If:

(1) .......................................................................................................... Carrier Level Reduces More Than -3 dB

(2) ................................................................................................... Modulation Level Reduces More Than -4 dB

(3) ...................................................................................................................................................Keying Ceases

(4) ..............................................................................................................................Incorrect Identification Code

Keying Features

- Microprocessor controlled for ease of programming

- Programmable generation of 1, 2, 3 or 4 Morse letters or numbers

- Programmable frame length of 5-16 seconds

- Programmable sequence repetition

- Programmable standby codes

NOTE:

Technical specifications established at 500 watts RF power into a 50-ohm load unless otherwise specified.

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Nautel's ND family of radiobeacon transmitters are identified by a multi-part identifier. This identifier is stamped on the transmitter's nameplate and identifies a specific configuration of radiobeacon in accordance with the following:

Figure 1-2 Nautel's Identification

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500 WATT RADIOBEACON TRANSMITTER

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Table 1-3 Test Equipment and Special Tools

NOMENCLATURE PART, MODEL, OR TYPE NUMBER APPLICATION (EQUIVALENTS MAY BE USED)

Dummy Load Resistive 50-ohm dummy load rated at

1000 watts (twice the power rating of the transmitter)

Provides precise 50-ohm load during calibration and trouble shooting.

Digital Voltmeter Any good quality 3 1/2 digit digital

voltmeter

Measure voltages/resistances during trouble shooting procedures

AC Voltmeter HP400E Precise measurement of RF voltage

across dummy load during calibration procedures

DC Ammeter 50 amperes measurement capability Precise measurement of DC current

consumption by power amplifiers during calibration

Oscilloscope Any good quality oscilloscope with a

calibrated time base

Monitor waveforms during testing and trouble shooting procedures

Audio Signal Generator 600 ohm impedance Simulate voice audio during testing

and calibration

Variable DC Power Supply

0-50 Volts DC Vary DC voltages (B- and +15

Volts DC) during calibration

Stop Watch Stop Watch Monitor keyer timing of coded

information during testing and calibration

Frequency Counter Any good frequency counter with an

accuracy of five parts per million up to 10

Measure audio and RF frequency during testing and trouble shooting.

MHz

Variac Variable Power Transformer Vary 230 volt AC input during

special calibration

Standard Electronic Tool Kit

Minimum requirements – various size screwdrivers and nut-drivers

Harmonic Filter Adjustment

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Table 1-4 Glossary of Terms

TERM DESCRIPTION

Bit Basic timing increment derived from master clock in keying

unit. Nominally 125 milliseconds long

Character Letter or number in the beacon identification signal

Element Smallest divisible part of a character. May be either a dot or

a dash

Frame Selected, fixed interval of time which is sufficiently long to

accommodate the beacon identification signal and an interval of continuous tone. Normally set to 64 bits (eight seconds)

ICAO International Civil Aviation Organization

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SECTION 2

THEORY OF OPERATION

GENERAL

2.1 The theory of operation for the subject

transmitter is presented in this section. The information is presented in detail using the electrical schematics as a reference.

TRANSMITTER DESCRIPTION (see figures SD-1 and SD-2)

2.2 The transmitter operates in the LF/MF band (190 kHz to 535 kHz) at 500 watts maximum (carrier) power. It automatically transmits specific beacon identification signals at a repetition rate of 8.0 seconds. Standby codes may also be transmitted when commanded from an external source. Provision is made for local or remote operation of the transmitter. Emission is continuous carrier with double sideband amplitude modulation modes, A2A beacon-keyed identification tone and A2A and A3E, simultaneous beacon and voice. Provision is also made for automatic changeover from the selected main side of the transmitter to the standby side when the selected main side's critical parameters are not met.

Outputs, from tapped current shunt resistors R1/R4, provide dc current indication on meter that are representative of the current being consumed by side

A or B of the transmitter. Current

A Cal potentiometer R2 and Current B Cal

potentiometer R3 provide adjustment for a precise dc current indications during special calibration procedures (side A or side B). Links between terminals 1/2 and 3/4 on TB3 are either connected or removed, dependent on the status (removed or installed) of optional battery panel A11.

CONTROL/MONITOR PANEL (A1) (see figure SD-3)

2.3 Control/monitor panel A1 contains switched metering circuits that monitor forward power, reflected power, modulation percentage, dc operating voltages and dc current of both sides of the transmitter. The monitor also contains alarm lamps, which turn on, when the following conditions exists;

overmodulation, high SWR, standby status and

shutdown status. A battery alarm, when turned on,

TEST-Volts/Current

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15 January 2005

indicates the transmitter's B- operating voltage is being produced by an external dc power source (battery etc).

The RF monitor connector provides a BNC coaxial connection for external test equipment to monitor a sample of the RF output of the transmitter. Other switching controls included are; local or remote selection, monitor (changeover inhibit), RF on/off and a select

SELECT MAIN Tx switch (side-A or side-B

selection). Individual circuit descriptions are as follows:

2.3.1 LOCAL/REMOTE CONTROL: The local/remote switching circuit controls the electrical power for the transmitter when the

ON. During normal operation, the CONTROL switch

is set to

REMOTE and REMOTE lamp is turned on.

RF switch is set to

Power trim A/B function and on/off switching facility can be controlled from a remote location. An external A/B main select (ground) on A1P4-11, when present, changes the selected main-side. When changeover occurs, remote and local standby alarm signals are generated. The

STANDBY-ALARM lamp shall turn on.

2.3.2 NORMAL/BYPASS CONTROL: During normal operation the set to

NORMAL. When the MONITOR switch is set to

BYPASS, the BYPASS lamp will turn on. A control

MONITOR switch will be

signal (ground) will be passed through connector A1P4-10 and applied to the monitor PWB. The automatic changeover circuits (main to standby) within the monitor PWB will be inhibited. When the

MONITOR switch is set to NORMAL, the BYPASS lamp

will turn off and the changeover circuits will no longer be inhibited.

2.3.3 RF CONTROL SWITCH: The RF switch controls the

ON/OFF function of the transmitter

and resets the transmitter to the selected main-side when set to

OFF then ON (if the transmitter is

operating in the standby-side, transmitter will automatically be reset to the selected main-side). The

RF ON status lamp will turn on when the RF switch is

set to

ON.

500 WATT RADIOBEACON TRANSMITTER

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2.3.4 ALARM LAMPS: The following paragraphs explain each alarm lamp function:

2.3.4.1 Battery-Alarm Lamp: The

ALARM lamp is normally turned off. When the B-

BATTERY-

operating voltage for the transmitter is produced by an external dc power source (battery, etc.), a battery control (+15 V dc) signal will be applied through connector A1P4-1 and passed to the anode of

BATTERY-ALARM lamp. The alarm-lamp will turn on.

2.3.4.2 RF Current-Alarm Lamp: The

CURRENT ALARM lamp is normally turned off. When

the modulation level is too high, as sensed by the RF current probe at the harmonic filter's input, +15 V dc shall be applied through connector A1P5-12 to the anode of the on. The

RF CURRENT lamp. The lamp will turn

RF CURRENT ALARM lamp shall also turn on

if the antenna impedance is less than 50 ohms at the sideband frequency and the antenna current is exceeding the level expected under normal (50 ohm) conditions.

2.3.4.3 SWR-Alarm Lamp: The

SWR-ALARM

lamp is normally turned off. When a reflected power ratio in excess of 2:1 has been sensed at the output of the harmonic filter, +15 V dc shall be applied through connector A1P4-9 and passed to the anode of the

SWR-ALARM lamp. The alarm-lamp will turn on.

2.3.4.4 Standby-Alarm Lamp: The

ALARM lamp is normally off. When the selected main

STANDBY

side turns off (caused by a fault on the selected mainside or a standby test control signal from a remote location), a B- control signal will be applied through connector A1P3-5 and passed to the

STANDBY-ALARM

lamp. The alarm-lamp will turn on.

2.3.4.5 Shutdown-Alarm Lamp: The

SHUTDOWN ALARM lamp is normally turned off.

When the subject transmitter's main and standby sides have turned off, a B- control signal will be applied through connector A1P4-12 and passed to the cathode of the

SHUTDOWN-ALARM lamp. The alarm-lamp will

turn on. The be turned on prior to the

STANDBY-ALARM lamp shall normally

SHUTDOWN-ALARM lamp

turning on.

2.3.5 SELECT MAIN TX SWITCHING: The

SELECT MAIN TX switch selects which side of the

subject transmitter will be the main operating side or

B. When set to A, the A side will be the selected

main-side and the

B side will be the standby. Either

side may be selected for the main-side. The Boperating voltage, from side

A and side B of the

transmitter are interfaced through the selected contacts of the switch and passed to their respective destinations.

2.3.6 SWITCHED METERING: The switched metering circuit contains with an associated switch and a

a TEST-Power/Mod meter

TEST-Volts/Current

meter with its associated switch. The following is a description of the metering circuits:

2.3.6.1 Test-Power/Mod Meter/Switch: The

TEST-Power/Mod meter provides an indication of the

parameter (forward power, reflected power or modulation) selected by the When it is set to out.

SET 100% MOD potentiometer (located on the

OFF, the meter movement is shorted

TEST-Power/Mod switch.

monitor PWB) is adjusted for 100% modulation indication on the meter when the switch is set to

SET.

MOD

2.3.6.2 Test Volts/Current Meter/Test Switch:

TEST-Volts/Current meter provides an indication

The (for both sides of the transmitter) of the parameter (BVdc, +24 V dc, +15 V dc, -15 V dc and dc current), as selected by the When it is set to

TEST-Volts/ Current TEST switch.

OFF, the meter movement is shorted

out. Potentiometer A1A1R2 is adjusted for a precise voltage indication on the meter when the switch is set to

B-V (Side A or Side B).

MODULATOR/POWER AMPLIFIER MODULE

2.4 There are two identical modulator/power

amplifier modules (A2 and A3) in the transmitter. Only one of them will be in use during operation. Modulator/power amplifier A2 will be selected when the

SELECT MAIN TX switch is set to A, modulator/

power amplifier A3 will be selected when it is set to

B. See figure SD-4 for the electrical schematic and

figure MD-4 through MD-9 for assembly detail.

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A modulator/power amplifier can provide up to 2000 watts of peak envelope power or 500 watts of continuous carrier power, over a frequency range of 190 kHz to 535 kHz. Each modulator/power amplifier contains four identical modulator assemblies (A1, A3, A5 and A7), four identical power amplifier assemblies (A2, A4, A6 and A8) and a display interface PWB (A9).

2.4.1 MODULATOR (A2A1) (see figure SD-4): The description for the four modulators are identical. Only modulator A1 will be explained. Modulator PWB assembly A1A1, power MOSFET A1Q1 and their associated components form a switched regulator circuit that changes the logic level of the variable width modulator drive pulses from a ground reference to a B- voltage reference (logic 0).

2.4.1.1 The mod drive (0 to +15 V dc pulses) on J1-1 is applied to switching transistor A1A1Q1. A1A1Q1 will switch on/off as the 0 to +15 VDC pulses are applied to its emitter. The output on its collector will be passed to transistors A1A1Q2/Q3. The bases of A1A1Q2/Q3 will be switching between the B- level and a voltage that is 13 V less negative than the B-level.

Transistors A1A1Q2/Q3 and their associated components form a balanced drive for power MOSFET transistor A1Q1. Zener diode A1A1CR1 and resistor A1A1R2 establish a reference voltage that is 13 VDC less negative than the B- voltage, this reference is applied to the collector of transistor A1A1Q2. When the bases of transistors A1A1Q2/Q3 are at B- level, A1A1Q2 will be turned off and A1A1Q3 will be turned on. The voltage at the emitter junction of transistors A1A1Q2/A1Q3 will be at the B-level, MOSFET A1Q1 will be switched off. When the bases of transistors A1A1Q2/Q3 are 13 volts less negative than the B- level, A1A1Q2 will be turned on, A1A1Q3 will be turned off, MOSFET A1Q1 will be switched on. The output at the emitter of A1A1Q2/Q3 will be a rectangular waveform at the pulse width modulator switching frequency and shall be switching between the B-voltage and a level that is 13 VDC less negative.

2.4.1.2 Zener diode A1A1CR1 maintains the voltage on the collector of A1A1Q2 at 13.0 V dc (logic 1) more positive than the B- voltage (logic 0), regardless of the state of transistor A1A1Q2, this ensures the voltage across the gate/source junction of

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MOSFET A1Q1 does not exceed 13.0 V. Transistors A1A1Q2/Q3 act as switches between a logic 1 and a logic 0 to charge and discharge the capacitive load presented by the gate of MOSFET A1Q1. MOSFET A1Q1 acts as a switch that connects its load to the Bline when turned on and to ground when turned off.

2.4.1.2.1 When a logic 1 is applied to the base of transistors A1A1Q2/Q3, A1A1Q2 will be forward biased (turned on) and A1A1Q3 will be reverse biased (turned off). A logic 1 will be applied to the gate of MOSFET A1Q1 and it will turn on. When MOSFET A1Q1 is turned on, current will flow through inductor A1L1.

2.4.1.2.2 When a logic 0 is applied to the bases of transistors A1A1Q2/Q3, A1A1Q2 will be reverse biased (turned off) and A1A1Q3 will be forward biased (turned on). A logic 0 will be applied to the gate of MOSFET A1Q1 and it will turn off. Current in inductor A1L1 will collapse through free wheeling diodes A1CR1/CR2.

2.4.1.3 Inductors A1L1 and L1 and capacitors C2/C3 form a low pass filter which removes the switching frequency (70 kHz) but allows audio information (300 to 3000 Hz) to pass without attenuation. The resultant output of the low pass filter is a negative dc voltage that varies at the frequency and amplitude of the modulating audio being applied. The level of the negative voltage is the average of the fixed width pulses (from the modulator driver) required to produce the desired RF carrier output from the transmitter when there is no modulation present. The superimposed audio's frequency is determined by the rate the pulse width changes. The amplitude is determined by the amount the pulse width differs from the fixed width of the reference pulses.

2.4.1.4 The

PA VOLTS 1 lamp monitors the output

of modulator A2A1. It will be full brilliance when the output power level is at maximum (125 watts). The average voltage of the four modulators may be monitored at test point TP1.

2.4.2 POWER AMPLIFIER (A2A2): The description for the four power amplifiers are identical. Only power amplifier A2A2 will be explained. The RF drive input on A2J1 is applied to the primary windings of 8:4 step-down transformer A2T1. The output of each secondary winding is applied across the gate and source terminals of a power MOSFET transistor. When the gate of MOSFET A2Q1 is

500 WATT RADIOBEACON TRANSMITTER

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positive, the gate of MOSFET A2Q4 will be positive, the gates of MOSFETS A2Q2/Q3 will be negative. MOSFETS A2Q1/Q4 will be turned on, MOSFETS A2Q2/Q3 will be turned off. A hot carrier diode, placed across the source/drain junction of each MOSFET, ensures switching transients do not damage the MOSFET transistors.

2.4.2.1 The secondary windings of transformer A2T1 are configured to ensure the RF voltage applied to MOSFETS A2Q1/Q4 and MOSFETS A2Q2/Q3 are in phase. The voltage applied to A2Q1/Q4 is 180 degrees out of phase with the voltage applied to A2Q2/Q3. When A2Q1/Q4 are turned on, A2Q2/Q3 will be turned off. Current will flow from the modulation voltage through the drain/source junction of MOSFET Q1, through the primary windings of transformer T1, through the drain/source junction of Q4 to ground. During the next half cycle, A2Q1/Q4 are turned off, A2Q2/Q3 will be turned on. Current will flow from the modulation voltage through the drain/source junction of A2Q3, in the reverse direction through the primary windings of transformer T1, through the drain/source junction of A2Q2 to ground. The resultant RF output (125 watts maximum) on the secondary of transformer T1 is essentially a square wave at the RF carrier frequency. This output is combined with output of the three associated power amplifiers (A4/A6/A8) and applied to connector J1 (500 watts maximum).

2.4.2.2 When the temperature in a module reaches 82°C, thermal switch S1 opens and inhibits the mod drive input on TB1-3. Thermal switch S1 closes when the temperature falls below 82°C. The

SUPPLY lamp shall turn on when the B- voltage is

B- DC

present.

EXCITER MODULE

2.5 There are two identical exciter modules

(A4 and A5) in the transmitter. Only one will be used during operation. Exciter A4 will be selected when the

SELECT MAIN TX switch is set to A, exciter A5 will

be selected when it is set to

B. An exciter module

contains a keyer (A1) which provides the modulating audio; a modulator driver (A2) which produces a 70 kHz, variable pulse width, mod drive output containing the carrier level and modulation information; an RF frequency generator (A3) which may be a fixed frequency, crystal-controlled RF oscillator or a DDS RF synthesizer; an RF drive

amplifier (A4) which increases the RF drive to the power level required by the modulator/power amplifier stage and regulated +15 V and -15 V power supplies. See figure SD-5 for electrical schematic and figures MD-13 through MD-16 for assembly detail.

2.5.1 +15 VDC REGULATOR: The +15.0 VDC regulator contains regulator A4U1 and its associated components. If regulator A4U1's output exceeds +16.0 VDC, current will flow through resistor A4R7 to the gate of thyristor A4Q1. Thyristor A4Q1 will turn on clamping the +24 V dc input at A4J2-2 to ground. The regulated +15 V dc can be checked on the

TEST-Volts/Current meter.

2.5.2 -15 VDC REGULATOR: The -15.0 V dc circuit contains zener diode A4R1 and its associated components. When the

RF switch is turned on, the B-

voltage is applied through A4J2-1 to diode A4CR1. Zener diode A4CR1 ensures the -15.0 V does not exceed the required limits. The regulated -15.0 V can be checked on the

TEST-Volts/Current meter.

2.5.3 KEYING/MOD SWITCH: Keying/mod switching circuit contains

MOD switch A4S2. During normal operation, both

switches will be in their

KEYING switch is set to OFF, a +15.0 V dc control

KEYING switch A4S1 and

ON position. When the

signal will be applied to circuits within the keyer PWB. When the

KEYING switch is set to ON, the

+15.0 V dc control signal will be inhibited. When the

MOD switch is set to ON, A +15.0 V dc control signal

will be applied to modulator driver PWB A4A2. When the

MOD switch is set to OFF, the +15.0 V dc

control signal will be inhibited.

2.5.4 POWER TRIM:

POWER TRIM

potentiometer A4R5 provides a means of decreasing the carrier level of the transmitter while maintaining the modulation percentage. Adjustment of the

POWER TRIM potentiometer may be performed

without gaining access to the transmitter cabinet's interior. The power trim function may be controlled locally or remotely.

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2.5.5 KEYER PWB (A4A1): (See figure SD-6) The keyer is a self-contained logic block that automatically generates keyed audio tone signals that are used to modulate the transmitter. This is accomplished by means of a 64/80/96-bit code cycle or frame, which is between 5 and 16 seconds long. The beacon identification signal is programmed in the keyer and may contain up to 4 characters (letters or numbers) followed by either a long space or a long filler dash to the end of the code cycle. The length of a dot is determined by dividing the frame length by the number of bits. For example, an 8second frame and 64 bits yield 125ms bits. A dash is 3 bits long while a dot is 1 bit long. A tone oscillator circuit capable of generating a 400 Hz or 1020 Hz tone is also contained on the keyer PWB with an associated keying gate. In addition to the actual beacon identification letters or numbers, two separate minor variations to the code may be selected via external controls.

These coding variations are referred to as standby '1' and standby '2' and may be used to transmit information such as changeover from selected main to standby transmitter or changeover of the power source from ac supply to the (optional) battery backup or diesel backup. The keyer also has the capability to generate whole frames of tones or spaces to meet particular customer coding requirements. If the transmitter is in the MCW operating mode, a keying override signal is applied to override the coded keying and actuate a continuous tone as the keyed tone output.

The keyer consists of four alphanumeric displays, two EEPROMs, four push-button switches, a tone generator, a watchdog circuit, and a reset circuit.

2.2.3.1 Each

COMmon input (pin 18) on

alphanumeric displays U11 through U14 is connected to programmed microcontroller U8 through two transistors which are used as level converters. All other alphanumeric display pins are connected to U8 via Darlington transistor arrays U2 and U3. LED segments of the alphanumeric displays are turned on by controlling U8’s output pins. As a power-saving feature, software will shut off the alphanumeric displays after the keyer has output 255 bits. To turn the display back on, any of the four push-button switches can be pressed.

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2.2.3.2 Each EEPROM (U9 and U10) has three inputs (

S, C and D) and an output (Q). The three

inputs are tied to the corresponding pin on the alternate EEPROM and connected to microcontroller U8, while the output of each EEPROM is connected to a unique input on U8. This writes the same information to both EEPROMs. When a read is conducted, software checks to see if the EEPROMs respond with the same information. If not, an error is indicated.

2.2.3.3 The four push-button switches (S1 through S4) are connected to microcontroller U8 via pull up resistors. A low indicates that the button is pushed.

2.2.3.4 A supervisory circuit (U15) is used to hold the reset (

RST) input (pin 10) high for 350 ms

(minimum) at initial turn-on. The circuit holds the reset high whenever the +5 V dc supply falls below

4.6 V. The reset pin is held high until the voltage increases above 4.6 V, or for a minimum of 350 ms, whichever period of time is longer.

2.2.3.5 The watchdog circuit consists of capacitors C19/C20, diodes CR7/CR8 and resistor R48. During normal operation, the P0.6 output (pin 37) on microcontroller U8 switches on and off at a high frequency. A low is provided, by the watchdog circuit, to Q10’s base. The keyer fault output (J2-2) will be open circuit. When a fault occurs, the keyer fault output switches to ground potential (Q10 turned on). When shorting jumper E4 is installed in the

ENBL position (shorting pins 1 and 2), the fault

acts to inhibit the keyed tone output (J1-1). When shorting jumper E4 is installed in the

DSBL position

(shorting pins 2 and 3), the fault, although indicated by

KEYER FAULT lamp DS1, has no effect on the

keyed tone output.

2.2.3.6 Operational amplifiers U1A/U1B and their associated components form a stable, free running audio oscillator. Positioning of shorting jumpers E1 and E2 in the feedback network allows frequencies of 400 Hz or 1020 Hz to be used for beacon tone (E1 and E2 shorting pins 1 and 2 provides a 1020 Hz tone; E1 and E2 shorting pins 2 and 3 provides a 400 Hz tone). To enable an external tone input (J2-1), shorting jumper E3 must be installed in the

EXT position (shorting pins 2 and

3) to disable the free running oscillator.

500 WATT RADIOBEACON TRANSMITTER

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2.5.6 RF OSCILLATOR PWB (A4A3) (see figure SD-9): The RF oscillator PWB is a dual purpose low level RF drive source for the exciter. It contains a crystal controlled oscillator circuit that can be connected as the RF drive generator and it contains a buffer/isolation amplifier that will accept and process an externally produced RF drive at the assigned carrier frequency. Links on the PWB are user connected to enable the integral crystal controlled oscillator and use it as the RF drive source or to enable the buffer/isolation amplifier when an external exciter is the RF drive source.

2.5.6.1 Crystal Oscillator: The crystal oscillator consists of transistor Q2, quartz crystal Y1, isolation amplifier Q3, frequency divider U1, buffer amplifiers Q4/Q5 and their associated components. When the crystal oscillator is to be the RF drive source, it must be enabled and the buffer amplifier must be inhibited. The crystal oscillator is enabled by linking pad pad

B. Pad D must not be linked to any other pad to

A to

inhibit the buffer amplifier. The crystal oscillator operates within the frequency band of 2.0MHz and

4.0MHz. Its Crystal (Y1) frequency must be 4 (4ƒc), 8 (8ƒc) or 16 (16ƒc) times the carrier frequency, whichever results in a frequency within the operating band. Variable capacitor C10 is adjusted to precisely set the oscillator to the desired frequency. The output of the oscillator is buffered by Q3 and applied to 12bit binary counter U1, as its clock. Pad

E is linked to

the divider pad which will provide the assigned carrier frequency (/ kHz,

4 when ƒc is between 500 kHz and 535

/8 when ƒc is between 250 kHz and 500 kHz or

/16 when ƒc is between 190 kHz and 250 kHz). Pad F must not be linked to pad E. Q4/Q5, which are

connected as a balanced drive, current amplify the selected output of U1. The resultant RF drive at J1-4 will be a 15 volt peak-to-peak square wave at the carrier frequency (ƒc).

2.5.6.2 External RF Drive Input: Circuitry consisting of Q1, U2, U3, U4 and their associated compnents are not used in ND radiobeacons.

2.5.7 RF SYNTHESIZER PWB (A4A3) (see RF synthesizer PWB manual, following section 10 of this manual): The RF synthesizer PWB uses direct digital synthesis (DDS) to generate the assigned carrier frequency within the radio beacon broadcast band (190 kHz to 535 kHz). The output of a digital synthesizer integrated circuit with internal high-speed

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12-bit digital to analog converter is low-pass filtered to provide a sinusoidal continuous output. The sine wave is digitized and divided by a factor of four to obtain the carrier frequency.

2.5.8 RF DRIVE AMPLIFIER (A4A4): The low level RF drive, a square wave switching between ground and 13.5 volts peak at the carrier frequency, is passed through connector A4A4J1 and applied to the primary winding of 1:1 coupling transformer A4T1. Transformer A4T1 has two identical sets of secondary windings, one wire of each set is connected to the gate and one wire of each set is connected to the source of power MOSFET transistors A4Q1/Q2. MOSFETS A4Q1/Q2 are connected in a push-pull configuration with the phasing of their inputs determining which one will be turned on.

2.5.8.1 When the gate of MOSFET A4Q1 is positive, the gate of MOSFET A4Q2 will be negative. A4Q1 will be on/A4Q2 will be off. The negative voltage Tx on (B- VDC) input at J2-1 will be applied through A4L1 and A4Q1 to A4Q1/Q2's drain/source junction. During the next half cycle, the polarity on the gates of A4Q1 and A4Q2 will reverse. A4Q1 will be off/A4Q2 will be on. A ground will be applied to A4Q1/Q2's drain/source junction. The output at A4Q1/Q2's source/drain junction will be a square wave switching between ground and B- VDC, at the carrier frequency.

2.5.8.2 The output from A4Q1/Q2 is applied through A4C3/C4/R1 to A4J2 as a 48-52 volt peak-topeak square wave RF Drive output for the RF power amplifiers. It is also peak detected by CR1 and applied to A4J3 as the RF Drive Level reference. This output is a dc voltage (between 12 and 16 V dc) that is proportional to the amplitude of the RF drive. Inductor A4L1 and capacitors A4C1/C2 provide decoupling for the Tx On (B- VDC) input. Diode A4CR2 provides protection against transient voltages in excess of 39 volts.

2.5.9 MODULATOR DRIVER PWB (A4A2) (see figures SD-7 and SD-8): The modulator driver processes the voice audio input and passes it to an emission mode multiplexer where it is multiplexed with a keyed tone from the keyer, depending on the emission mode selected (keyed tone or keyed tone/voice). The modulator driver produces a pulse width modulated mod drive that contains the carrier

500 WATT RADIOBEACON TRANSMITTER

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level and audio information. Logic circuits monitor RF drive level and modulation pulse width output. They turn on the appropriate

DRIVE ALARM

The

AUDIO LIMITER lamp will flash when audio

lamp if a fault threshold is exceeded.

MOD DRIVE and/or RF

peak/trough thresholds are exceeded.

2.5.9.1 Voice Audio Filter: The voice audio input on J1-4 is applied across varistor RV1 and

LEVEL potentiometer R2 and passed to the non-

VOICE

inverting input of operational amplifier U1A. Varistor RV1 provides protection against high-level interference transients (e.g., lightning). Op amps U1A/U1B and their associated components form low and high pass four-pole filter circuits. The filters define the lower and upper limits of the audio bandwidth of the subject transmitter at 300 to 3000 Hz respectively.

2.5.9.2 Voice Audio Amplifier/Limiter: Resistor R14 in series with the voice signal forms an attenuator with JFET Q1 which acts as an audio limiter and is turned on by unusually high peaks of the audio signal. This improves the voice power of the transmitter by compressing high voice peaks and preventing overmodulation on high peaks. Limiting of both positive and negative peaks of voice is provided since after amplification by operational amplifier U2A, the total signal is applied to inverting comparator U3B and non-inverting comparator U3A which turn on JFET Q1 when comparator thresholds are exceeded by voice signal peaks. Operation of either comparator also switches U3D which will turn on the

LIMITER lamp, indicating the occurrence of a voice

AUDIO

peak and limiter action. The voice signal is then applied through

VOICE MOD % potentiometer R21 and

passed to emission mode multiplexer U4. Test point TP2 provides a monitoring point for the voice signal after filtering and limiting.

2.5.9.3 Emission Mode Multiplexer: The voice audio and/or the keyed tone are selected as the

modulating audio output, for each emission mode, by emission mode multiplexer U4. The binary sum of the mod enable and press-to-talk inputs select the appropriate gate of U4 (0/1-no audio, 2-keyed tone and voice, 3-keyed tone only). The level of the keyed tone audio is adjusted by the setting of

TONE LEVEL

potentiometer R19 determines the keyed tone level when keyed tone only is selected. The setting of

TONE MOD % potentiometer R20 determines its level

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when keyed tone and voice are selected.

% potentiometer R21 is adjusted for the voice

VOICE MOD

modulation level. A ground potential press-to-talk command will apply a logic 0 to U4-A.

2.5.9.4 Line Volts Compensation/Power Trim Control: Line volts compensation and power trim

control circuits contain wideband monolithic analog multiplier U6, operational amplifiers U5A, U5B and U2B and their associated components. The audio output of the emission mode multi-plexer, the B-VDC and power trim inputs are converted to current inputs and applied to U6-8/5/1 respectively. The output on U6-4 is applied to U5B and converted to a voltage on U5B's output. If the B- voltage decreases, the output voltage at U5B-7 will increase proportionally, similarly if the B- voltage increases, the voltage on U5B-7 will decrease proportionally. When the power trim control signal on J2-2 decreases, the output voltage on U5B-7 will decrease and visa-versa. Resultant modulation depth will remain constant regardless of B- voltage variations and power trim variations to -3dB.

2.5.9.5 PWM Square-Wave Generator: The pulse-width modulator square wave generator contains programmable timer U8 and its associated components. The oscillator frequency is adjusted to a nominal frequency of 70 kHz by

FREQ variable

capacitor C22. The output of the generator will be a 15 volt square wave at the oscillator frequency and will be applied to the ramp integrator circuit.

2.5.9.6 Ramp Integrator: The ramp integrator circuit contains operational amplifier U9B plus its associated components. The 15 volt square wave from the PWM square wave generator is applied to the inverting input of U9B. Capacitor C26 and resistor R63, which are located in the feedback circuit of U9B, result in a linear sawtooth waveform being produced at the output of U9B. TP5 provides a convenient location to measure the waveform.

ADJUST

potentiometer R58 is adjusted to set the

RAMP

negative going peaks of the linear waveform to a DC reference potential of zero volts.

500 WATT RADIOBEACON TRANSMITTER

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Figure 2-1 Simplified Schematic of Pulse-Width Differential Amplifier

2.5.9.7 Linear Attenuator: The linear attenuator circuit contains operational amplifier U7A, unity gain amplifier U7B, transistors Q2/Q4 and their associated components. U7A and Q4 form a diode to ground circuit which results in a bias voltage of approximately 0.6 volts DC being applied to the emitter of Q2. Normally the VSWR cutback input at J2-1, which is applied to U7B's non-inverting input, is 0 volts. U7B's output will be 0 volts and Q2 will be reverse biased (turned off). The linear attenuator circuit will present high impedance between the audio signal and ground. When a positive voltage VSWR cutback input is applied, U7B's output will be positive and forward bias Q2 (turn it on). The impedance of the linear attenuator circuit will decrease in proportion to the current flow through Q2. The attenuation factor will vary in proportion to the positive voltage level of the VSWR cutback input.

2.5.9.8 Variable Pulse-Width Generator: The variable pulse-width generator circuit is a differential amplifier that compares the linear sawtooth waveform from the ramp integrator with the linear attenuated audio and produces a nominal 70 kHz rectangular waveform as its pulse-width modulation output. The circuit comprises operational amplifier U9A, transistors Q5, Q6 and their associated components. They are configured to form an emitter coupled differential amplifier. A portion of the audio and DC signal is applied to the non-inverting input of U9A from the wiper of

O/P POWER potentiometer R48.

Unity gain buffer amplifier applies this voltage to the base of Q6. The sawtooth waveform from U9A is applied to the base of Q5. Refer to figure 2-1 for a simplified schematic of the differential amplifier.

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2.5.9.9 For explanation purposes, assume the audio signal is a DC reference voltage that does not contain an audio component. When the sawtooth waveform is less positive than the DC reference voltage, Q5 will be reverse biased and Q6 will be forward biased. When the sawtooth waveform is more positive than the DC reference voltage, Q6 will be reverse biased and Q5 will be forward biased. The output at the collector of Q6 will be approximately zero volts DC when Q6 is forward biased and +15 volts DC when it is reverse biased.

The forward/reverse bias ratio of Q6 is determined by the audio level. When audio is superimposed on the DC reference voltage, the input applied to the base of Q6 will go more or less positive at the audio rate. The magnitude of the change will be determined by the audio component's polarity and amplitude. When it is less positive, Q6 will be reverse biased for a longer portion of the sawtooth waveform. When it is more positive, Q6 will be reverse biased for a shorter portion of the sawtooth waveform. When audio is present, the resulting pulse-width modulated output, at the collector of Q6, is a varying width, rectangular waveform at the square wave generator's repetition rate (nominally 70 kHz).

2.5.9.10 Balanced Drive: The balanced drive is a switching circuit that is driven by the variable pulsewidth modulation output of the variable pulse-width generator. The circuit contains buffer amplifier U10A, transistors Q7 and Q8 and their associated components. The pulse-width modulated signal is inverted by buffer amplifier U10A. Transistors Q7 and Q8 turn on and off at the PWM switching frequency. The switching action of transistors Q7/Q8

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

ensures the leading and trailing edges of the rectangular waveform are sharp. The mod drive output at J2-6 is a low impedance pulse-width modulated signal switching between +15 volts dc and ground.

2.5.9.11 Pulse-Width Fault Detector: The pulse-width fault detector circuit monitors the pulsewidth modulation signal for the presence of +15 V dc pulses. The circuit contains operational amplifier U11B, inverter U10D, relay K1 and their associated components. A two-pole low pass filter, comprising R68/R69 and C30/C31, continuously monitors the average on/off ratio of the variable pulse width mod drive signal. Normally the voltage on C31, which is applied to U11B's non-inverting input, will not exceed the reference threshold voltage being applied to its inverting input from the junction of R70/R71. U11B's output will be at near ground potential, resulting in the U10D's output being +15 V dc. A mod drive alarm signal will not be applied to J2-4.

If a dangerously high variable pulse width on/off ratio should occur, the voltage on capacitor C31 will exceed the reference threshold voltage applied to U11B's inverting input. U11B's output will be +15 V dc. Relay K1 will energize and remove the mod drive output from J2-6. U10D's output will be

ALARM zero volts dc. A zero potential mod drive

MOD DRIVE

alarm signal will be applied through J2-4 to and turn on the lamp (A4DS3).

2.5.9.12 RF Drive Alarm Circuit: The RF drive alarm circuit contains operational amplifier U11A, inverter/buffers U10B/U10C, transistor Q3 and their associated components. When the transmitter is turned on, the voltage at the junction of C25/R60 will instantly rise to +15 V dc and decay slowly through resistors R60/R61. Transistor Q3 will be forward biased (turned on) and U11A-3's non-inverting input will be at ground. Resistors R64/R65 establish the threshold voltage on U11A's inverting input.

The output on U11A-1 will be low and output on U10B-2 will be high, causing diode CR3 to be forward biased. The input on operational amplifier U10A-7 will be high and its output low.

The low output on U10A-6 will inhibit the mod drive. The output of U10C-4 will be low and applied to the RF drive alarm lamp on the exciter's front panel. The

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RF drive alarm lamp will turn on. After approximately five seconds the voltage being applied to the base of transistor Q3 will decay through resistors R60/R61, transistor Q3 will be reversed biased, the output of U10B-2 will go low, diode CR3 will be reversed biased. The mod drive output on J26 will no longer be inhibited. The output of U10C-4 will go high and the RF drive alarm lamp on the exciter's front panel will turn off.

POWER ON/OFF PANEL ASSEMBLY (A6) (see figure SD-1)

2.6 The power on/off panel assembly contains the

POWER-AC LINE and POWER-BATTERY switches.

Under normal operating conditions both switches will be set to their

ON position. AC power from the

service entrance is applied through terminals 1 and 2 on TB1 and passed to the contacts of the

LINE switch. When it is set to ON, 230 V ac will be

POWER-AC

passed to power supply modules A7 and A8. The DC power (battery) source is applied from TB2-2(-), through fuse A6F1 and the contacts of the

BATTERY switch to battery panel (optional) A11. If

POWER-

the optional battery panel is installed, DC power will be inhibited by switching circuits within the subject transmitter until AC power fails or decreases below a low AC voltage threshold.

POWER SUPPLY MODULES (see figure SD-10)

2.7 There are two identical power supply

modules (A7 and A8) in the transmitter. Only one of the power supplies will be in use during operation. Power supply A7 will be selected when the

MAIN TX switch is set to A, power supply A8 will be

selected when it is set to

SELECT

2.7.1 POWER SUPPLY CONTROL PWB (A7A1): 230 V ac from the service entrance, at J1-

1/2, is passed through the appropriate fuses (dependent on 50 or 60 Hz) to the tapped primary winding of power transformer T1. T1 contains two sets of centre-tapped secondary windings. One set provides a low level (17.5-0-17.5) ac for use as a phasing reference and as the voltage source for a 15 V dc regulated power supply. The other set provides a higher level ac as the voltage source for the B- Vdc power supply. Varistors RV1/RV2 provide transient protection. Thyristors Q1/Q2, form a controlled fullwave rectifier for the B- Vdc. The B- Vdc output is maintained at the required level by controlling their

500 WATT RADIOBEACON TRANSMITTER

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gate voltage and therefore their on time for each half cycle of the ac voltage source.

2.7.1.1 Diodes A1CR1/CR2 full-wave rectify the ac voltage from T1's low level centre-tapped secondary and (T1-11/T1-12) and produce an unfiltered DC voltage (nominally 23 V dc) with a ripple frequency of twice the frequency of the ac power source. This voltage is applied through diode A1CR3, filtered by A1C2 and applied to +15 VDC regulator A1U1. The output of A1U1 will be a regulated 15 V dc. Zener diode A1CR5 provides protection for A1U1 against transients in excess of 30 volts.

2.7.1.2 The unfiltered ripple dc from full-wave rectifier A1CR1/CR2 is also applied to the noninverting input of zero crossing detector A1U2A. Zener diode A1CR4 and resistor A1R3 for a limiter to restrict the voltage being applied to A1U2A-3 to +10 volts. Resistors A1R6/R7 establish a low level on A1U2A's inverting input. This results in a narrow output pulse on A1U2A-1 when the zero crossing of the ac voltage occurs. At the zero crossing, A1U2A's output will be low, A1CR7 will be forward biased and A1C4 will quickly discharge to ground potential.

2.7.1.3 When the non-inverting input of A1U2A rises to a level more positive than the voltage on A1U2A's inverting input, diode A1CR7 will be reversed biased. Capacitor A1C4 will charge towards +15 VDC, through A1R8, at an exponential rate. The input at A1U2D's non-inverting input will be a sawtooth waveform.

2.7.1.4 Operational amplifier A1U2C and its associated components provide a DC reference that is proportional to the B- Vdc output at J1-3/4/5. A1R2/R4 form a voltage divider between +15 V dc and B- Vdc The resultant voltage at the junction of A1R2/R4 (+5.9 V dc when B- Vdc is -50 V dc) is applied to the inverting input of A1U2C. An adjustable reference voltage is applied to A1U2C's non-inverting input (by A1R12's wiper) from the voltage divider formed by A1R11/R12/R13. A1R12

is adjusted for a DC voltage that will maintain A1U2C's output (DC reference voltage) at a level that will result in a B- VDC output of 50.0 V dc by controlling the on-time of thyristors Q1/Q2. If the BVDC starts to go less negative, A1U2C's inverting input will go more positive and its dc reference voltage output will go less positive.

A1U2C's dc reference voltage is applied to A1U2D's inverting input where it is compared with the voltage of the sawtooth waveform on A1U2D's non-inverting input. At the start of each sawtooth waveform, A1U2D's inverting input will be more positive than its non-inverting input and its output will be a 0.0 V dc. When the sawtooth waveform's voltage is more positive than the dc reference voltage (A1U2D's inverting input is less positive than its non-inverting input) A1U2D's output will switch to +15 V dc for the balance of the sawtooth waveform's period. The more positive the DC reference voltage is, the shorter the period of time A1U2D's output will be 15 V dc.

A turn-on delay circuit, formed by A5A1C6/R20/ CR10/R19/CR11, applies +15 V dc to U2D's inverting input at the instant of turn-on. It ensures the sawtooth waveform's more positive periods are minimal during the initial charge period of the BVDC storage capacitors in the modulator/power amplifier modules. The delay voltage decreases exponentially as C6 charges. When it goes less positive than the output of U2C, U2C's output will assume control and the delay circuit will have no further influence.

2.7.1.5 When A1U2D's output is +15 V dc, A1Q1 and A1Q2 will both be forward biased (turned on). Whichever thyristor (A1Q1 or A1Q2) has a positive voltage half cycle on its anode will be forward biased and turn on for the balance of the half-cycle. Capacitors C1 and C2 prevent the thyristors from false firing and diodes A1CR8/CR9 prevent reverse bias between the collectors and emitters of transistors A1Q1/Q2 when thyristors Q1/Q2 are turned off. Thyristors Q1/Q2 will be gated off each time zero crossover occurs on the full-wave waveform.

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2.7.2 B- VDC To +24 VOLT DC CONVERTER PWB (A7A2): The B- voltage is

applied through fuse A7F1 and inductor A2L1 to the emitter of A2A1Q1. When B- VDC reaches approximately -40 V dc, A2A1Q1 will be forward biased and turn on. The resultant output from the collector of A2A1Q1 will cause A2A1Q2 to be forward biased and turn on. The voltage at the junction of resistor A2A1R6 and the collector of A2A1Q2 will go to a nominal 13.0 V dc more positive than the B- voltage and be applied to timer A2A1U1. Resistors A2A1R7 through A2A1R10, diode A2A1CR2 and capacitor A2A1C2 determine the switching frequency and duty cycle being generated by timer A2A1U1. The output of A2A1U1, an adjustable pulse width control signal, is passed to the gate of power MOSFET A2Q1.

2.7.2.1 Power MOSFET A2Q1, inductor A2L3, diode A2CR1 and capacitor A2C2 form a basic stepdown flyback converter which inverts the polarity of the source voltage. When power MOSFET A2Q1 switches on, current from capacitor A2C2 will be applied to the load while current from power MOSFET A2Q1 will store energy in inductor A2L3. When power MOSFET A2Q1 switches off, the stored energy in inductor A2L3 will be applied through diode A2CR1 and capacitor A2C2 and applied to the load. This ensures that a constant current will be applied to the load when power MOSFET A2Q1 is switching on and off. Zener diode A2CR2 protects against excessive voltage on the output when the load is removed and resistor A2R3 limits the peak current through power MOSFET A2Q1. The output from the converter circuit, a +24.0 V dc control signal, is passed through resistor A2R4 to +24 V status lamp DS1. The lamp will turn on. The +24.0 V dc control signal is also passed to A2TB1-5 for external use.

2.7.2.2 The -15 V dc generated by components A2L3, A2CR3 and A2C3 is not used in ND radio beacons.

2.7.3 AC SUPPLY MONITOR (A7A3) ASSEMBLY: The AC supply monitor circuit

contains transistors A3Q1/A3Q2/A3Q4, power MOSFET transistor A3Q3 and their associated components. Under normal operating conditions (ac power source), the breakdown threshold of zener diode A3CR3 will be exceeded, transistors A3Q1/A3Q4 and MOSFET A3Q3 will be forward

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biased (turned on). Transistor A3Q2 will be reverse biased (turned off). +15 V dc will be passed to ac sense connectors J1-8 and J1-12. Diodes A3CR1/ CR2 and capacitor A3C1 form a full-wave filtered rectifier for the input voltage to the ac supply monitor PWB. Resistors A3R1/R2 provide attenuation. If the breakdown threshold of zener diode A3CR3 is not exceeded, transistor A1Q1 will be reverse biased (turned off). When transistor A3Q1 turns off, transistor A3Q2 will be forward biased (turned on). MOSFET A3Q3 will be reverse biased (turned off) and transistor A3Q4 will be reverse biased (turned off). The AC sense outputs on connectors J1-8/J1-12 will be inhibited. The transmitter will either switch to the standby side, providing the fault is not generated from the AC power source of if already operating on the standby side, will switch to the dc power source (battery, if installed).

HARMONIC FILTER ASSEMBLY (A9) (see figure SD-11)

2.8 The harmonic filter assembly is a band pass filter that attenuates the harmonics of the square wave output being applied from the modulator/power amplifier circuits. The filter has a flat response characteristic over the operating bandwidth. The circuit also filters out the frequency on the lower side of the carrier frequency. Relay K1 or relay K2 will be energized depending on which side

A or B of the

subject transmitter has been selected. The harmonic filter assembly contains a forward/reflected power probe (A9A2) and an RF current probe (A9A1).

2.8.1 RF CURRENT PROBE (A9A1): The RF current probe contains transformer A1T1 and its associated components. The probe monitors the RF output current. The RF input from the contacts of relay K1 or K2 is passed across the primary winding of transformer A1T1 and applied to terminal '1' of inductor L1. A sample of the RF current is applied across transformer A1T1's secondary winding and passed through resistors A1R1 through A1R4 to connector A1J2. The current sample is passed to logic circuits within the monitor/interface panel.

500 WATT RADIOBEACON TRANSMITTER

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2.8.2 FWD/REFL POWER PROBE (A9A2): Voltage transformer A2T1, current transformer A2T2 and their associated components provide voltage and current arms of a forward/reflected power bridge, which samples the RF output signal. Current transformer A2T3 and a secondary winding of transformer A2T1 provide voltage or current waveform outputs (as selected by

RF MON switch) for

monitoring purposes. The anti-phase voltages developed across A2T2's secondary are summed with the voltage from A2T1 to provide DC voltages at the cathodes of A2CR1/CR2 which are proportional to the forward/reflected power. A2R1 through A2R8 provide 50 ohm loading for their respective transformers.

2.8.2.1 RF MON Switching:

RF MON switch

A2S1 allows selection of either the voltage or the current waveform to be monitored on RF monitor BNC connector J1 on control/monitor A1's front panel. The following provides the necessary information for the setting of the

RF MON switch.

2.8.2.2 The high capacitive reactance of the antenna is tuned at the carrier frequency by the ATU loading coils to produce a series resonant circuit. The resulting net antenna resistance is transformed to 50 ohms in a matching transformer to provide the load impedance required by the transmitter. When the antenna is very short, compared with the carrier frequency's wavelength, the series resonant circuit has an extremely high Q. Under these conditions, a perfect match may occur at the carrier frequency, but the sidebands may be mismatched, causing a standing wave on the feed cable at the sideband frequencies.

2.8.2.3 Depending upon the length of the feed cable, the impedance at the sideband frequencies may appear higher or lower than 50 ohms. If the sideband impedance appears low, the current waveform should be selected by

RF MON switch to prevent excessive

current overloading. If the sideband impedance appears high, the voltage waveform should be selected by

RF MON switch to prevent excessive

voltages occurring at the sideband frequency. The correct setting of

RF MON switch is made by choosing

the waveform which displays the greater modulation depth.

2.8.2.4 The use of an inefficient antenna produces a bandpass filter effect which reduces the modulation depth of the radiated signal.

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2.8.2.5 Under no circumstances should the modulation level, as measured by the current or voltage probe, be adjusted beyond 95 % in an effort to offset the sideband attenuation which occurs in the antenna. This will cause excessive dissipation and distortion to occur and would create spurious emissions which do not comply with national and/or international specifications.

MONITOR PWB (A10)

(see figures SD-12 and

SD-13)

2.9 The monitor PWB monitors critical parameters of the subject transmitter and produces control signals which turn on display lamps when these parameters are not met or a status condition of the transmitter is to be known. The PWB also produces and applies external alarm and status control signals to a remote location for the user's information. Test switches, located on the PWB, can be set to enable calibration/repair on one side of the transmitter while the other side is operating normally.

The monitor PWB provides adjustments for the carrier and modulation thresholds, sets the changeover time delay (seconds) and produces the unmetered +15 V dc and -15 V dc for the subject transmitter. The board also provides control signal outputs for the forward/reflected power (remote and local) and produces control signal outputs for the battery, SWR, shutdown, standby and RF current alarm circuits.

2.9.1 TEST SWITCH CONTROL: Under normal operating conditions

TEST A switch S2 are set to NORMAL. When either is

set to

TEST, the RF output from that side A or B will

TEST B switch S1 and

be inhibited and it will be operating into an open circuit. The switches are normally set to

TEST when

performing maintenance procedures.

2.9.2 RELAY SWITCHING: The relay switching circuits contains remote on/off relay K1, shutdown relay K2, standby relay K3 and A/B main select relay K4. The following paragraphs describe each relay switching circuit:

2.9.2.1 Remote On/Off Relay: If the transmitter is set to local control, the remote on/off relay will have no influence. During normal operations, when remote is selected, relay K1 will be de-energized (transmitter turned on). When a remote ground

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

control signal is applied to 'remote off' input J4-1, relay K1 will energize, the B- operating voltage will be inhibited. A 'reset enable' (ground) control signal will be applied to circuitry on the monitor PWB. The

STANDBY ALARM and SHUTDOWN-ALARM lamps will

turn on. External shutdown and standby alarm control signals will be generated.

2.9.2.2 A/B Main Select: The A/B main select relay (K2) is used to select which side of the transmitter (A or B) is the 'main' side. When the transmitter is set to local control, the relay is controlled by the select main

XMTR switch (S3) on the

control panel (A1). When the transmitter is set to remote control, the relay is controlled by an external input on the A/B main select remote line (J2-5). Relay K2 is de-energized to select side A as the main side.

2.9.2.3 Shutdown Relay: During normal operation, relay K2 will be energized. If the ground control input on K2-13 is removed, relay K2 will deenergize. The transmitter will turn off. A B- control signal will be applied through J5-12 causing the

SHUTDOWN-ALARM lamp to turn on and an external

shutdown alarm control signal (ground) will be generated at J4-5.

2.9.2.4 Standby Relay: During normal operation, relay K3 will be energized. If the ground on K3-13 is removed, K3 will de-energize. The B- voltage will be applied through J3-5. The

STANDBY-ALARM lamp

shall turn on and an external standby-alarm control signal (ground) will be generated and passed to standby alarm (remote) on J4-3. The transmitter's selected main side will shut down and the standby side will turn on.

2.9.3 MONITOR +15 VOLT DC REGULATOR: +24 V dc is applied through J6-11

or J6-4 (from either the

A or B side of the transmitter)

and passed through its associated diode to +15 V dc regulator U12-3. +24 V dc is applied to J6-12 for external use. The regulated +15 V dc is applied to J8-9 for external use and circuits within the transmitter for internal use. TP13 provides a convenient location to measure the +15 V dc.

2.9.4 MONITOR -15 VOLTS DC CIRCUIT: The B- voltage is applied across resistor R74 and zener diode CR16. The two components provide -15 VDC for the transmitter. TP9 provides a convenient location to measure the -15 V dc. Transistors Q10/Q11 plus their associated components provide a sharp on/off transition for the -15 V dc. If the Binput is less negative than -30 V dc, zener diode CR13 will be reverse biased and turned off. Q10 will be reverse biased and turned off. When Q10 is turned off, Q11 will be forward biased and turned on. -15 V dc will be clamped to ground. When the B- Vdc is turned off, the transmitter will reset (return to the main side) in a nominal five seconds.

2.9.5 MOD THRESHOLD CIRCUIT: The fwd pwr input on J6-1 a dc voltage representing the forward power of the transmitter with a super imposed ac voltage proportional to the modulation depth, is applied through loading resistors R1/R2 and buffer amplifier U1A to the

MOD THRSH potentiometer is normally set for the

MOD THRSH potentiometer.

desired minimum modulation level (normally to detect a -4.0 dB drop on the intended modulation depth). The detected dc voltage (level of dc voltage will depend on setting of

MOD THRSH potentiometer),

from the wiper of R7, is applied through Q1/Q2 to the junction of C7/R26.

2.9.5.1 Amplifiers U3B through U3D form a buffered 'OR' circuit for the keyed tone input thus allowing provision for a keyed tone input to JFET Q3 from side

A or side B. JFET Q3 and the 'OR' circuit

form a synchronous detector which will only detect signals that are in phase with the keyed tone inputs to U3B or U3C. The detected dc voltage is applied to the non-inverting input of comparator U4A where it is compared to a bias voltage, established by resistors R28/31/33, being applied to the inverting input of U4A. When the inverting input is more positive than the bias voltage on the non-inverting input of operation amplifier U4A, U4A's output will be ground. The output of U4A will be a switched voltage that goes to ground each time the detected DC input (modulation) becomes more positive than the inverting input.

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2.9.5.2 The output from operational amplifier U4A is applied across a differentiating circuit consisting of resistor R38 and capacitor C12. The differentiating circuit produces a positive pulse, during each transition, which is applied to the base of transistor Q6. If the positive pulse from U4A is not present (loss of keying or a decrease of 4.0 dB on the intended modulation depth) on the base of transistor Q6 before the changeover circuit's time delay has elapsed, transistor Q6 will remain turned off. This will cause the transmitter to change over to the standby side, indicated by a shutdown condition, indicated by a

ALARM lamp turning on, if the standby side was

STANDBY-ALARM lamp turn on; or

SHUTDOWN-

providing the RF drive.

2.9.6 CARRIER THRESHOLD CIRCUIT: The fwd pwr input on J6-1, a dc voltage representing the forward power of the transmitter with a super imposed ac voltage proportional to the modulation depth, is applied through loading resistors R1/R2 and buffer amplifier U1A to the potentiometer R18. The

CARR THRSH potentiometer

CARR THRSH

is normally set for the desired minimum carrier level (normally to detect a -3.0 dB drop on the intended carrier level). The detected dc voltage (level of dc voltage will depend on setting of the

CARR THRSH

potentiometer) from the wiper of potentiometer R18 is applied across capacitor C8.

2.9.6.1 Capacitor C8 filters out the modulation component of the RF carrier and charges to the mean dc level, representative of the RF carrier level. This reference voltage is passed to the non-inverting input of comparator U3A and represents the carrier threshold level. It is compared to the voltage level, established by resistors R22/25, on the inverting input of U3A. Normally, the output of U3A will be high impedance to ground and the circuit will have no influence. When the output of U3A switches to low impedance to ground, the positive pulses from modulation comparator U4A will be inhibited.

2.9.6.2 If the positive pulse from U4A is not present (modulation depth decrease of 4.0 dB) on the base of Q6 before the changeover circuit's time delay has elapsed, Q6 will remain turned off. This will cause a change over to the standby exciter (

ALARM lamp shall turn on) or a shutdown

(

SHUTDOWN-ALARM lamp shall turn on) if the

STANDBY-

standby exciter was providing the RF drive.

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2.9.7 CHANGEOVER DELAY CIRCUIT: The changeover delay circuit can be adjusted for a changeover time delay of between 20 and 80 seconds. The time it takes for capacitors C15/C16 to exceed the voltage level established on the inverting input of comparator U5A will depend upon the setting of the

CHANGEOVER DELAY potentiometer. With the

potentiometer set for a maximum time delay (80 seconds), capacitors C15/C16 will take 80 seconds before the voltage level established on the noninverting input of comparator U5A is more positive than the inverting input. When this occurs, comparator U5A's output will switch to high impedance, a changeover control signal will be applied to the base of transistor Q8.

A high SWR status control signal being applied to diode CR8 will cause it to be forward biased and turn on. Q6 will be forward biased and ensure capacitor C15/C16 are held at ground potential. This results in the changeover circuits being inhibited during a high SWR condition.

2.9.8 STANDBY CIRCUIT: Under normal operating conditions transistor Q8 will be reversed biased and turned off. The changeover circuit will be inhibited. If a fault occurs resulting in transistor Q8 being turned on, a low control signal will be applied through inverters U6A/U6B and applied through resistor R61 to the base of transistor Q9. Q9 will be forward biased and turn on.

The input to U7-3 will be high and output on U7-1 will be high. The output on U7A-1 will be applied through resistor R77 to the base of transistor Q13. Transistor Q13 will be reversed biased and turn off. A changeover control signal will be applied to K3 and turn on a standby-alarm lamp on the control/monitor panel. The transmitter will automatically switch to the standby side.

2.9.9 SHUTDOWN CIRCUIT: Normally, the control signal applied to flip-flop device U7-11 will be low and the shutdown circuit will be inhibited. If a fault occurs when the standby side of the transmitter has been selected, the collector of transistor Q9 will switch to a ground level.

After a nominal delay (ten seconds), caused by resistor R67 and capacitors C24/C27, the input on flip-flop device U7-11 will go high. The output on U7B-13 will be high and applied through R75 to the

500 WATT RADIOBEACON TRANSMITTER

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base of transistor Q12. Transistor Q12 will be reverse biased and turn off. A shutdown control signal will be applied to relay K2 and to a shutdown-alarm lamp on the control/monitor's front panel. The lamp will turn on. Both sides of the subject transmitter will be shutdown.

2.9.10 FORWARD POWER CAL: The fwd pwr input on connector J6-1, a dc voltage representing the forward power of the transmitter with a super imposed AC voltage proportional to the modulation depth, is applied through loading resistors R1/R2 and applied to the non-inverting input of buffer amplifier U1B. Capacitor C6 filters the modulation component while charging to a dc level that is representative of the carrier level. The output of buffer amplifier U1B is applied through resistor R78 and the

FWD PWR CAL

potentiometer and passed through connector J5-3 to

TEST meter M1 on control/ monitor A1's front panel.

The

FWD PWR CAL potentiometer provides a

calibration adjustment for the forward power indication on the

TEST meter.

The dc voltage representing the transmitters RF carrier level is also passed through operational amplifier U1C. Operational amplifier U1C plus its associated components provide a gain of five at the output of U1C-8 which is applied across diodes CR5/6 to fwd pwr (remote) connector J6-3 for external use.

2.9.11 AUDIO MONITOR CIRCUIT: The fwd pwr input on connector J6-1, a dc voltage representing the forward power of the transmitter with a super imposed ac voltage proportional to the modulation depth, is applied through loading resistors R1/R2 and passed to the non-inverting input of audio amplifier U2A. The output on U2A-1 is coupled through capacitor C23 and passed to audio monitor connector J10.

2.9.11.1 Speaker Control: Normally the switch will be set to

OFF. When it is set to ON, an

audible signal will be passed through the

VOLUME

potentiometer and passed to SPEAKER LS1.

SPEAKER

2.9.12 RF CURRENT CIRCUIT: The purpose

of the RF current circuit is to provide an indication (

RF CURRENT ALARM) that the modulation level is too

high. It actually detects that a threshold has been reached where the RF current (on the troughs of the modulated envelope) reduces to near zero. This in

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turn protects the transmitter from excessive peak current which would occur on the peaks of the modulation envelope.

A sample of the RF current is applied through RF current sample connector J8-12 and passed to a detector circuit consisting of diode CR1 and capacitor C3. The detected signal is passed across resistor R6 and a limiting circuit consisting of diode CR3 and resistor R12. The limiting circuit maintains the input on operational amplifier U8A inverting input to +15 volts dc. Resistor R20 and

OVERMOD CAL

potentiometer establish the reference threshold on the non-inverting input of operational amplifier U8A-3. Under normal operation the output of U8A-1 will be low, transistor Q4 will be reverse biased and turned off.

If the voltage being applied to U8A-2 becomes less positive than the reference voltage at U8A-3, the output on U8A-1 will go high. Transistor Q4 will be forward biased and turn on. Capacitor C13 will discharge causing the input on U8B-6 to become more positive than the reference voltage on U8B-5. The output on U8B-7 will go high. The

ALARM lamp shall turn on.

RF CURRENT-

2.9.13 SWR CUTBACK THRESHOLD CIRCUIT: Under normal operating conditions (no

reflected power), comparator U10A's output will be low (ground). The circuit will have no influence. If the voltage level (DC voltage representing the reflected power) on U10A's non-inverting input becomes more positive than U10A's inverting input (established by resistors R94/96 and the

CUTBACK THRESHOLD

potentiometer), U10A-1

SWR

output will go high. The voltage level, on U10A-1 output, will depend on the level of the DC voltage representing the reflected power sample on J8-4. Capacitor C43 shapes the transient response time providing a lower gain by connecting resistor R100 in parallel with resistor R101 to protect against unwanted fluctuations.

The output on U10A-1 is passed to SWR cutback connector J8-10 and applied to a linear attenuator circuit within the mod driver PWB. When U10A's output is high, comparator U10B's non-inverting input will be more positive than U10B's inverting input (approximately 0.6 V dc), established by resistor

R103 and diode CR31. The output on U10B-7 will

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

go high. This output will be passed to four separate circuits.

One portion of U10B's output will be applied to the base of transistor Q14. It will be forward biased and turn on. Q14's collector (ground) will be passed to connector J6-9 for external use. The output on U10B7 is also passed through inverter U6C to the cathode of diode CR39. When U6C's output is low (SWR present), diode CR39 will be forward biased and turn on. A ground will be passed to SWR standby connector J9-8 for internal use.

The control signal, representing a high SWR condition, on the output of U10B-7 will also be applied through buffer U4B and resistor R112 and passed to the changeover circuits to inhibit the subject transmitter from changing over when a high SWR condition is present. A fourth portion of the high SWR condition on the output U10B-7 will be applied through resistor R111 and passed through connector J5-9 and applied to a

SWR-alarm lamp on

the control/monitor's front panel. The

SWR alarm

SWR-alarm

lamp will turn on when a high SWR condition is present.

2.9.14 POWER TRIM INTERFACE CONTROL CIRCUIT: Operational amplifiers

U4C/D, U11A/B and their associated components form the power trim interface control circuit for sides A and B. Amplifiers U11A/B limit the output of U4C/D to a level that will not exceed the intended RF carrier output of either side (set by the respective

POWER

potentiometers on the mod drive PWBs). The

O/P

outputs of amplifiers U11A/B are applied through pwr trim connectors J6-10/5.

2.9.15 REFLECTED POWER/REFL PWR CAL CIRCUIT: A DC voltage representing the

reflected power of the transmitter is passed through refl pwr connector J8-4 and applied through load resistors R90/91 to the inverting input of buffer amplifier U9D. Capacitor C37 will charge through resistor R92 to an average value representing the reflected power. The output of U9D is applied through resistor R104 and the

REFL PWR CAL

potentiometer and passed to refl pwr connector J5-2 for internal use. The

REFL PWR CAL potentiometer

provides adjustment during calibration for the reflected power indication being provided by

TEST

meter M1 on control/monitor panel A1. The reflected power control signal from the output of U9D is also

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applied through buffer U1D and passed to refl pwr (remote) connector J8-1 for external use.

2.9.16 MOD% CONTROL CIRCUIT: Operational amplifier U9A and its associated components form a one-pole active low-pass filter/ attenuator. The input on J6-6, a DC voltage proportional to the intended carrier level, is applied through the filter/attenuator where the RF carrier frequency will be removed but the audio information will be passed.

One output of U9A is applied to U9B's non-inverting input. A second output is applied through R27 and the

SET 100% MOD potentiometer to A7-8. A peak

detector, comprising CR4, R40 and C10, detects the peak output on U9A. The detected signal is applied through buffer U9C to J7-7. When the set to

MOD-READ, the meter will be placed between

TEST switch is

the mod meter adjust line on J7-8 and the mod% on J7-7. For 100% adjustment on the test meter,

TEST

switch on the control/monitor panel is set to mod-set, the output on U9C will be double the output of U9A to compensate for the return line through the meter from the output of U9A.

2.9.17 AC POWER MONITOR CIRCUIT (DC Option Installed): The AC power monitor circuit

controls the status of the local and remote battery alarm indications when the DC power source option is installed.

When the AC power is satisfactory, a +15 VDC AC sense input will be on J8-8/7. U6E output will be low and control/monitor panel's

BATTERY-ALARM lamp

will be off. The output of inverter/buffer U6D will be maintained at a low (0.0 V dc) and transistor Q15 will be reverse biased (turned off). An open collector will be applied to J6-8 as the remote battery alarm output.

When the AC power fails, the AC sense input on J8-8/7 will be 10K ohms to ground. U6E-12 will be high and the control/monitor panel's

BATTERY-ALARM

lamp will turn on. The output of inverter/ buffer U6D will be high (+15 V dc) and transistor Q15 will be forward biased (turned on). A current sink to ground will be applied to J6-8 as the remote battery alarm output.

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

2.9.18 AC POWER MONITOR CIRCUIT (Dc Option Not Installed): When the dc power source option is not installed, the output of the ac power monitor circuit is paralleled with the output of the SWR cutback circuit.

When the ac power is satisfactory, a +15 V dc ac sense input will be present on J8-8/7 and the output of inverter/buffer U6D will be maintained at a low (zero VDC). Diode CR29 will be reverse biased and the monitor circuit will have no influence on the SWR cutback output.

When the ac power falls fifteen percent below its normal level, the ac sense input on J8-8/7 will be 10K ohms to ground and the output of inverter/ buffer U6D will be held high (+15 V dc). Diode CR29 will be forward biased and the monitor circuit will apply +15 V dc to U10B-5 and to J8-10. The +15 V dc SWR cutback output will cause the RF output to cutback to a minimal level and the SWR cutback circuit will respond as if a high SWR is being detected (see paragraph 2.9.3.15). The A/B changeover circuit will be inhibited, the control/ monitor panel's

ALARM lamp will turn on, a current sink to ground

SWR-

will be applied to J6-9 as the remote SWR alarm output and a low (zero V dc) will be applied to J9-8 as the SWR standby output. This status will be maintained until the ac power is within 10 percent of its normal nominal level and the ac sense input returns to +15 V dc.

2.9.19 MONITOR BYPASS CIRCUIT: Under normal operating conditions the monitor bypass input on J5-10 will be an open circuit. The bypass circuit will have no influence. If a monitor bypass high (+15 V dc) control signal is applied to the base of Q16, transistor Q8's base will be held at ground potential regardless of the output from comparator U5A. The changeover circuit will be inhibited and the transmitter will remain operating in the selected side A or B.

BATTERY CONTROL PANEL (A11) ASSEMBLY (see figure SD-14)

2.10 Battery control panel assembly contains

sensing circuits which automatically switch the external power source from ac to dc (battery) if the ac voltage falls below the required limits or if both the main-side and standby-side power supply modules fail. Once the transmitter has switched to the dc power source (battery), sensing circuits monitor the battery voltage and will inhibit the dc power source (battery) input if the B- falls below the desired low battery threshold level. The transmitter will shut down.

2.10.1 BATTERY CONTROL PWB (A11A1): The battery control PWB contains transistors A1Q1/ A1Q2 and their associated components. During normal operation (ac power source), transistors A1Q1/Q2 will be reverse biased (turned off) and relays K2/K3 will be de-energized. The battery input on connector J1-1/2/3 will be inhibited. The ac sense (A) and ac sense (B) inputs (+15.0 V dc) are applied through connectors P1-7/P1-5 and passed to the bases of transistors A1Q1/Q2. The B- Vdc (A)/B- Vdc (B) inputs are applied through connector P1-8 and P1-4, across zener diodes A1CR3/CR4 and to the bases of transistors A1Q1/A1Q2. A positive voltage will be developed on the bases of transistors A1Q1/Q2. A1Q1/Q2 will be reverse biased and turned off. If one AC sense input (A or B) is removed, the remaining AC sense input (A or B) will maintain the turned off status of transistors A1Q1/A1Q2. Relays K2/K3 shall remain de-energized.

If the selected main-side

A or B of the transmitter fails,

due to a failure of the associated power supply, the respective transistor (A1Q1-side A or A1Q2-side B) will remain turned off. The relay (K2 or K3) associated with transistor A1Q1 or A1Q2 will also remain de-energized. The transmitter will changeover and the B- VDC and ac sense inputs shall be provided from the standby-side power supply. If the standbyside of the transmitter's B- VDC power source fails (loss of both power supplies), transistors A1Q1/Q2 shall turn on and relays K2/K3 will energize. The battery will automatically provide the transmitter with the B- operating voltage (a momentarily dip in output power may occur). If the ac power source fails, the same result will occur that was explained for the loss of both power supplies.

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500 WATT RADIOBEACON TRANSMITTER

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2.10.1.1 Low Battery Voltage Monitor: When operating from an external dc power source (battery), the AC sense inputs on P1-7 and P1-5 are removed. Transistors A1Q1/A1Q2 are turned on and relays K2/K3 energized. If the battery voltage discharges below the desired Low Battery Threshold (nominally

-42 V dc), transistors A1Q1/Q2 shall turn off. Relays K2/K3 shall de-energize and the transmitter will shut down. Potentiometers A1R7/R8 set the bias level on the bases of transistors A1Q1/Q2 and therefore establish the desired Low Battery Threshold (adjusted at the factory when -42 volts DC is present on the anodes of zener diodes A1CR3/ A1CR4).

2.10.1.1.1 Recharging of the dc power source (battery) will not result in the transmitter automatically turning on.

2.10.1.1.2

BATTERY RESET switch S1 must be

momentarily closed (ground) for a nominal three to five seconds. When

BATTERY RESET switch S1 is

momentarily closed, relay K1 will momentarily energize and the associated modulator's storage capacitors will begin to charge through limiting resistors R2/R3 towards the battery voltage. The BVdc (B) and B- Vdc (A) output on connectors J112/J1-10 are inhibited by the contacts of relay K1. When the B- Vdc levels on connectors P1-8/P1-4 reach the desired level (greater than -42 V dc), transistors A1Q1/A1Q2 will be forward biased (turned on). Relays K2/K3 will energize and the transmitter will resume normal operation on the selected main-side (A or B, dependent on the position of the

SELECT MAIN TX switch) using the dc power

source as the transmitter's B- supply.

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500 WATT RADIOBEACON TRANSMITTER ND2000A-02X-xx0

SECTION 3

INSTALLATION AND PREPARATION FOR USE

GENERAL

3.1 This section contains the information

required to prepare the equipment site to receive the subject transmitter and the information required to unpack, install and prepare the transmitter for use.

3.1.1 VISUAL INSPECTION: It is recommended that a visual inspection be performed on the subject transmitter, removable modules and associated printed wiring boards prior to installation and applying power. Inspect for the following:

(a) Inspect all electrical components for evidence of

overheating or physical damage.

(b) Verify all fuses are the correct value and are not

defective.

mechanical bond and adequate solder.

(d) Verify all wiring insulation is not pinched,

frayed, broken or otherwise damaged.

(e) Verify wire strands of wiring conductors are not

broken or otherwise damaged.

(f) Verify the chassis and printed wiring boards are

free from solder slivers and other conductive foreign objects.

(g) Verify all integrated circuit devices are installed

and firmly seated in their sockets.

TEST EQUIPMENT

3.2 The test equipment required for initial

installation is listed in table 1-3.

SITE REQUIREMENTS

3.3 The transmitter should be installed in a

building that provides a minimum clearance on all sides of at least four feet.

3.3.1 LIGHTNING/SAFETY GROUND: The transmitter site must contain a lightning/safety ground system to protect the transmitter from lightning induced voltage transients. Refer to the

Recommendations for Transmitter Site Preparation booklet.

3.3.2 ANTENNA SYSTEM: The antenna system must present a 50 ohm unbalanced load to the transmitter's RF output, with a maximum SWR of 2:1. Provision to protect the transmitter from lightning induced voltage transients must be incorporated. Refer to the Recommendations for Transmitter Site Preparation booklet.

3.3.3 ELECTRICAL POWER: The transmitter will operate from an ac or dc power source.

3.3.3.1 AC Power Requirements: The transmitter will operate from a 180 to 250 V RMS, 50 Hz, (line-to-neutral) or 180 to 250 V RMS, 60 Hz (line-to-line) ac power source, provided the mean voltage does not vary by more than ten percent. The ac power source must be rated at a minimum of 1200 VA. Provision must be made to protect the transmitter from lightning-induced voltage transients. Refer to the Recommendations for Transmitter Site Preparation booklet.

3.3.3.2 DC Power Requirements: If used, the dc power source must be a battery bank that provides a nominal -48.0 V dc with a constant current capacity of 20 A. The no-load voltage of the dc power source must be in excess of -42.0 V dc for the transmitter to turn on initially. The capacity of the dc battery bank, in conjunction with the Low Battery Voltage Threshold setting, shall dictate the length of time the transmitter will operate. When the battery bank voltage has decayed to below the low battery voltage threshold (-42.0 V dc, factory setting), the transmitter will turn off and prevent the batteries from fully discharging. It is recommended that the DC power source be separately fused. Provision must be made to protect the transmitter from lightning induced voltage transients.

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500 WATT RADIOBEACON TRANSMITTER ND2000A-02X-xx0

3.3.4 ELECTRICAL POWER CABLING: The ac power cable must be provided by the user. A dc power cable, (if applicable) must also be provided for the user. The ac power cable enters the cabinet through a cable entry hole in its lower, rear, righthand side and terminates at terminal board TB1. If applicable, the dc power cable enters the cabinet through a cable entry hole in its lower, rear, lefthand side and terminates at terminal board TB2 (see figure MD-38).

3.3.5 RF FEED CABLE: The RF feed cable must be a 50 ohm coaxial cable that is terminated by a type N coaxial connector. The RF output connector of the transmitter is located on the outer, top section of the transmitter cabinet.

3.3.6 CONTROL/MONITOR CABLING: The control/monitoring cable enters the cabinet through a cable entry hole on the top of the transmitter cabinet (left or right side), are passed through a ferrite toroid and terminate on terminal boards TB3 and TB4. The ferrite toroids are available at either end of the interface panel assembly (see figure MD-29) and provide protection for the transmitter from lightning induced voltage transients. Terminal boards TB3/TB4 are accessible from the rear of the transmitter cabinet. Refer to figure MD-38 for information to assist in determining cable length.

3.3.7 VENTILATION: The interior of the transmitter enclosure must contain a ventilation system that will ensure the inside temperature does not exceed +55°C.

3.3.8 HEATING: The interior of the transmitter enclosure must contain a heating system that will ensure the inside temperature does not go below 10°C.

3.3.9 WORK AREA: It is recommended that a suitable work area be provided adjacent to the transmitter to permit bench inspection/repair of removable assemblies.

EXTERNAL INPUT/OUTPUT CIRCUIT REQUIREMENTS (see figure 3-2):

3.4 The external input (audio and control) and

output (status and alarm monitoring) circuits must comply with the following:

3.4.1 EXTERNAL AUDIO SOURCE: An external audio source must be provided. The impedance of the audio source must be a balanced 600 ohms. The audio signal applied to the transmitter must be between -20 dBm and +20 dBm. The user determined limits are between 0 to 95 % modulation.

3.4.2 REMOTE CONTROL CIRCUITS: The transmitter's on/off status and its RF output level can be controlled remotely. There is also provision to remotely switch from main to standby, as a test function, to verify the standby transmitter is serviceable and to activate the standby '1' and standby '2' code variations. When these remote controls are used, the following must be observed:

3.4.2.1 Standby '1' and Standby '2' Controls: The stby 1 and stby 2 (side A and side B) switching circuits should be the equivalent of normally open, single pole, single throw switches. When in the closed position, each switch should apply a ground to the appropriate terminal of barrier strip TB3 (see figure 3-2).

3.4.2.2 Battery Reset Control: When required, the battery reset switch should be a normally open, single pole, single throw, spring-loaded switch. When held in its closed position, it shall apply a ground to TB3-17.

3.4.2.3 Power Trim 'A' and 'B' Controls: The A and B power trim control inputs are intended to be provided by a remote maintenance monitoring (RMM) system. It shall provide +15 volts DC to TB4-10 for side A and to TB4-11 for side B when the intended carrier level is desired. If an RMM system is not used, connect TB4-10 and TB4-11 to +15 volts DC.

3.4.2.4 Remote Off Control: The rmt off control switching circuit should be the equivalent of a normally open, single pole, single throw switch. When set to its closed position (tx off), it shall apply a ground to TB3-19.

3.4.2.5 A/B Main Select Control: The A/B main select switching circuit should be the equivalent of a normally open, single pole, single throw switch. When set to its closed position, it shall apply a ground to TB3-18.

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3.4.2.6 Press-To-Talk Control: The press-to-talk switching circuit should be the equivalent of a normally open, single pole, single throw switch. When set to its closed position (press-to-talk), it shall apply a ground to TB4-19. If the press-to-talk information is phantom fed on the audio input, this switching circuit will not be required (see note on figure SD-2).

3.4.3 EXTERNAL STATUS MONITORING: Outputs that may be used to identify or verify the status of remotely controlled functions are available on terminals of TB3 and TB4. These outputs include forward power, reflected power, modulation percentage, audio monitor, internal standby and SWR standby.

3.4.3.1 External Forward Power Monitoring: The external forward power output is intended to be monitored by a remote maintenance monitoring (RMM) system. A buffered dc voltage that is representative of the forward power level is provided at TB4-14. This voltage is a non-linear function of the forward power level and will be 7.8 ± 10% V dc at 500 watts. Any other terminating device must have an input impedance of not less than 100K ohms.

3.4.3.2 External Reflected Power Monitoring: The external reflected power output is intended to be monitored by a remote maintenance monitoring (RMM) system. A buffered dc voltage that is representative of the reflected power level is provided at TB4-15. This voltage is a non-linear function of the reflected power level and will be 8.6 ± 10% V dc at 500 watts. Any other terminating device must have an input impedance of not less than 100K ohms.

3.4.3.3 External Modulation Percentage Monitoring: The external modulation percentage

output is intended to be monitored by a remote maintenance monitoring (RMM) system. A buffered DC voltage that is representative of the modulation percentage is provided at TB4-16. When operating in CW, at 500 watts RF output, 4.3 ± 10% V dc will be applied to TB4-16. When operating in MCW, at 500 watts carrier power and 95% modulation, 8.2 ±10% volts dc will be applied to TB4-16.

3.4.3.4 Audio Monitor: A transformer coupled 600 ohm audio output is provided between TB3-22 and TB3-23 for external monitoring.

3.4.3.5 Internal Standby Monitoring: The internal standby output is the normally closed contact of a relay. The relay is held energized when the selected side (main transmitter) is operating and an open circuit is applied to TB3-9. When the main transmitter has been shut down and the standby transmitter has been enabled, the relay will deenergize and apply a ground to TB3-9.

3.4.3.6 SWR Standby Monitoring: The SWR standby output is provided by a CMOS inverter that is protected from negative voltages by a series diode. When the reflected power is satisfactory, an open collector is applied to TB3-10. When the reflected power is excessive and causing the carrier level to be cutback (reduced), a current sink-to-ground is applied to TB3-10.

3.4.4 EXTERNAL ALARM MONITORING CIRCUITS (see figure SD-1): Alarm signals that

identify malfunctions or conditions that require response from a maintainer are provided.

3.4.4.1 Standby-Alarm: A standby alarm output is provided by the normally closed contact of a relay. The relay is held energized when the selected side (main transmitter) is operating and an open circuit is applied to TB3-15 as the standby alarm status. When the selected side has shut down and the standby side has been enabled, the relay will de-energize and apply a ground to TB3-15 as the standby alarm status.

3.4.4.2 Shutdown-Alarm: A shutdown-alarm output is provided by the normally closed contact of a relay. The relay is held energized when either side (main or standby transmitter) is operating and an open circuit is applied to TB3-16 as the shutdown alarm status. When both sides have been shut down and the transmitter is off-the-air, the relay will de-energize and apply a ground to TB3-16 as the shutdown alarm status.

3.4.4.3 SWR-Alarm: The emitter/collector impedance of a switching transistor to ground is applied to TB3-13 as the SWR-alarm output. When the reflected power is satisfactory, the transistor will be reverse biased and apply an open collector to TB3-

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500 WATT RADIOBEACON TRANSMITTER ND2000A-02X-xx0

13 as the SWR alarm output. When the reflected power is excessive and causing the carrier level to be cutback (reduced), the transistor will be forward biased and a current sink-to-ground will be applied to TB3-13 as the SWR alarm output.

3.4.4.4 Battery Alarm: The emitter/collector impedance of a switching transistor to ground is applied to TB3-14 as the 'remote battery alarm' output. When ac power is being used as the transmitter's power source, the transistor will be reverse biased and apply an open collector to TB3-14 as the 'remote battery alarm' output. When the AC power fails or is turned off and an external dc power source (battery) is the transmitter's power source, the transistor will be forward biased and a current sink-to-ground will be applied to TB3-14 as the 'remote battery alarm' output.

NOTE

Current flow through a current sink (switching transistor) must not exceed 200 mA. Zener diodes are connected between the output and ground to ensure voltage transients, induced in the external wiring, are not coupled to the transmitter's logic circuits. The external alarm monitoring circuits must operate from a positive dc voltage power source. An external dc power supply may be used or +15 V dc from TB4-12 may be used as the voltage source. If the +15 V dc from TB4-12 is used, it must be remembered that this voltage is turned off if the transmitter is shut down.

UNPACKING:

3.5 The transmitter is packed in wooden crates

for shipment. A packing list(s) provides a detailed listing of crate contents.

Crates should be inspected for transit damage prior to shipment acceptance and/or uncrating.

3.5.1 TRANSMITTER CABINET CRATE: The transmitter is packed partially disassembled in a wooden crate that is approximately 178 cm (70 inches) x 74 cm (29 inches) x 76 cm (30 inches). Shipping weight is approximately 150 kilograms (330 pounds). Open crate and remove the transmitter cabinet as follows:

(a) Locate crate in an upright position, as marked,

in a clear area that will permit extraction of the transmitter without risk of damage to the unit or injury to personnel.

(b) Remove the panel identified as the top from the

crate by carefully prying it open using a small pry bar or other suitable tool.

transmitter and carefully remove the transmitter cabinet.

(d) Perform a visual inspection of the transmitter

cabinet and its assemblies ad detailed in paragraph 3.1.1.

3.5.2 POWER SUPPLY MODULE CRATE: The power supply modules are packed fully assembled in a wooden crate that is approximately 65 cm (25 inches) x 72 cm (28 inches) x 43 cm (17 inches). Shipping weight is approximately 110 kilograms (245 pounds). Open crate and remove modules as follows:

(a) Locate the crate in an upright position, as

marked on the crate, in a clear area that will permit extraction of the power supply modules without risk of damage to the unit or injury to personnel.

(b) Remove the panel identified as the top from the

crate by carefully prying it open using a small pry bar or other suitable tool.

modules and place at a location near the transmitter cabinet.

(d) Perform a visual inspection of power supply

modules as detailed in paragraph 3.1.1.

(e) Do not install power supply modules in

transmitter cabinet at this time.

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3.5.3 EXCITER AND MODULATOR/ POWER AMPLIFIER MODULE CRATE: The

exciter and modulator/power amplifier modules are packed fully assembled in a wooden crate that is approximately 114 cm (45 inches) x 58 cm (23 inches) x 35.5 cm (14 inches). Shipping weight is approximately 52.3 kilograms (115 pounds). Open crate and remove the modules as follows:

(a) Locate crate in an upright position, as marked

on crate, in a clear area that will permit extraction of modules without risk of damage to unit or injury to personnel.

(b) Remove the panel identified as the top from the

crate by carefully prying it open using a small pry bar or other suitable tool.

amplifier modules and two exciter modules. Place modules at a location near the transmitter cabinet.

(d) Perform a visual inspection of the subject

modules as detailed in paragraph 3.1.1.

(e) Do not install subject modules in transmitter

cabinet at this time.

ANCILLARY PARTS

3.6 An ancillary parts list is provided with each

transmitter. These parts include commonly used installation materials and hardware. The ancillary parts are not intended to be long term maintenance spares and are provided only to assist in the initial installation. An itemized listing of the ancillary parts kit contents is included in its packing list.

USER ASSIGNED INFORMATION

3.7 The final configuration of each transmitter

is determined by the user's requirements and applications. The following user assigned information must be obtained prior to final assembly and installation of the transmitter.

3.7.1 CARRIER FREQUENCY: Determine the transmitter's assigned carrier frequency and record frequency in the Established Reference section of table 5-2.

3.7.2 TONE FREQUENCY: Determine which keyed tone frequency (400 Hz, 1020 Hz) is to be used and record frequency in the Established Reference section of table 5.2.

3.7.3 IDENTIFICATION CODE: Determine the identification code that has been assigned to the transmitter and record code in the Established Reference section of table 5.2.

3.7.4 STANDBY CODES: Determine the standby codes as follows:

3.7.4.1 Standby 1 (A) Code: Determine the standby 1 (A) code variation to be transmitter and record code in the Established Reference section of table 5.2.

3.7.4.2 Standby 2 (A) Code: Determine the standby 2 (A) code and record code in the Established Reference section of table 5.2.

3.7.4.3 Standby 1 (B) Code: Determine the standby 1 (B) code variation and record code in the Established Reference section of table 5.2.

3.7.4.4 Standby 2 (B) Code: Determine the standby 2 (B) code and record code in the Established Reference section of table 5.2.

3.7.5 MEAN LEVEL OF AC POWER SOURCE: Determine the mean RMS voltage level

of the ac power source that will be applied to the transmitter.

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Table 3-1 Crystal Operating Frequencies

FREQUENCY (kHz) MULTIPLY BY CRYSTAL FREQUENCY (kHz)

190 - 250 16 3040 to 4000 251 - 500 8 2000 to 4000 501 - 535 4 2000 to 2140

PARTS REQUIRED BUT NOT SUPPLIED

3.8 Some parts required to complete the

subject transmitter's installation are not supplied with the transmitter. The user must supply these parts. A specific installation will dictate the parts required and will normally include the following:

(a) A suitable 50 ohm RF output coaxial cable,

terminated by a type 'N' coaxial connector at the transmitter end, is required.

(b) All external control/monitor wiring must be

provided by the user.

cabling must be provided by the user.

3.8.1 OSCILLATOR CRYSTALS: Two oscillator crystals are required if the RF drive is generated by the crystal controlled oscillator on the RF oscillator printed wiring boards. If the assigned carrier frequency is identified by the user and the oscillator crystals are ordered during manufacture, the crystals will be installed in the transmitter. If oscillator crystals are not ordered prior to shipment, they must be obtained by the user. The crystals must be fundamental, AT cut; with undercut pins for installation in a standard HC-6 holder. They must operate in a parallel resonant circuit, with a load capacitance of 50 pF. Crystal frequency must be between 2.0 MHz and 4.0 MHz (4, 8 or 16 times assigned carrier frequency - see table 3-1), with an initial frequency tolerance of ± 10 parts per million at 25°C and a frequency stability of ± 2 parts per million over an operating temperature range of 0°C to 50°C.

NOTE

It is recommended that at least one spare oscillator crystal be obtained as a replacement for maintenance purposes.

PRE-INSTALLATION PROCEDURES

3.9 Assembly of the transmitter must be

completed and the following pre-installation procedures completed prior to applying power.

3.9.1 DISASSEMBLY REQUIRED: Disassemble the transmitter to the extent required to gain access to its major assemblies and complete the pre-installation procedures as follows:

(a) Set or verify the

TEST meter indications are set

to zero.

(b) Verify battery links are connected if optional

battery panel (A11) is not installed or removed if the battery panel is installed (see note on figure SD-1).

3.9.2 EXCITER MODULE PREINSTALLATION (see figure MD-14): Determine if

the exciter modules contain an RF synthesizer PWB or an RF oscillator PWB [when RF drive is generated by an integral oscillator], then proceed as follows:

3.9.2.1 RF Synthesizer PWB Pre-Installation: If an RF synthesizer PWB has been installed as A3 in the exciter module, perform the pre-installation procedures completing the Preparation for Use section of the RF synthesizer PWB service instruction manual.

3.9.2.2 RF Oscillator PWB Pre-Installation: (see figure MD-19) If an RF oscillator PWB has been installed as A3 in the exciter module, complete the following requirements or verify they are being met:

(a) An oscillator crystal that meets the requirements

of paragraph 3.8.1 must be installed in crystal socket XY1.

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500 WATT RADIOBEACON TRANSMITTER ND2000A-02X-xx0

(b) A link must be connected between printed

wiring pad

A and pad B (enables crystal

controlled oscillator).

wiring pad

D and any other pad (disables

buffer/isolation amplifier).

(d) A link must not be connected between printed

wiring pad

F and any other pad.

(e) A link must be connected between printed

wiring pad

4, /8 or /16). Enter table 3-1 with carrier

E and the appropriate divide-by pad

frequency to determine divider.

3.9.3 KEYER PWB PRE-INSTALLATION: Complete the pre-installation procedures on keyer PWB A3 as follows (refer to figure MD-14 to locate the keyer PWB and to figure MD-17 for its assembly detail):

3.9.3.1 Keyer Content Configuration: Set up the keyer’s content (type, number of characters, standby code, character setting and frame length) as follows:

NOTE

The keyer PWB’s pushbutton switches S1 (up), S2 (left), S3 (right) and S4 (down), in conjunction with four alphanumeric displays, are used to configure the keyer’s contents. Pressing S2 and S3 simultaneously enters the setup menu. This menu is used to set up all aspects of the keyer. To navigate the setup menu, S1 increments, S4 decrements, S2 backs up, and S3 accepts and proceeds to the next selection.

(b) Select the keyer type, as indicated by the

alphanumeric displays, noting the options are

ICAO or TRAN. If TRAN is selected, proceed to

step (e), otherwise continue to step (c).

ICAO (International Civil Aviation

Organization) is a standard that allows the user to key any number of symbols (in this case, 1 to 4) using a variable bit/frame length (5 to 16 second frames). Standby code 1 inserts a space between predetermined letters when it is held low. When standby 2 is grounded, a blip is inserted before the first letter is keyed.

TRAN (Transport Canada) uses a 10-second

frame and 0.125ms bits to key out 3 symbols. When the standby 1 pin is held low, the space after the last letter and before the continuous tone is extended from 5 spaces to 9. When standby 1 and 2 pins are both held low, standby 1 is alternated. One frame will have the elongated space and the following frame will have the shorter space.

NOTE

The

KEYER FAULT lamp (DS1) may turn/be on

during keyer setup. It should turn off when the keyer is configured.

If an exclamation point (

!) is displayed on the

alphanumeric displays during keyer setup, an EEPROM error may exist.

ICAO keying only, select the number of

letters to be keyed, noting the options are

3 or 4.

1, 2,

(d) For

ICAO keying only, set up standby code '1',

noting the options are

1, 2, 3 or 4 [depending

on number of characters selected in step (c)], signifying the character that precedes the space.

(e) Set up each of the eight output frames by

selecting the frame type, noting the options are

(a) Enter the keyer’s setup menu by pressing S2

and S3 simultaneously.

keyed (

k), mark (M) or space (S).

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Table 3-2 Selecting Primary Winding Taps for Power Transformers A7T1/A8T1

VOLTAGE (RMS)

AC SUPPLY TRANSFORMER TAPS

(WIRE #5) (WIRE #6)

190 - 199 4 1 200 - 209 5 2 210 - 219 5 1 220 - 229 6 2 230 - 239 6 1 240 - 249 7 2 250 - 259 7 1

180 - 189 4 2

(f) Set up the specific characters to be keyed

(between 1 and 4 for

ICAO; 3 for TRAN),

noting the options are all alphanumeric characters (

0 to 9, A to Z)

(g) For

ICAO keying only, set up the frame length,

noting the options are between

5 and 16

seconds (typically 8 seconds).

3.9.3.2 Keyed Tone Frequency: If the keyed tone frequency is to be 1020 Hz, as determined in paragraph 3.6.2, install shorting jumpers E1 and E2 in the

1020 position (shorting pins 1 and 2). If keyed

tone frequency is to be 400 Hz, install shorting jumpers E1 and E2 in the

400 position (shorting pins 2

and 3).

3.9.3.3 Keyed Tone Source: If the keyed tone signal is to be supplied by the internal tone oscillator, install shorting jumper E3 in the

INT position (shorting

pins 1 and 2). If the keyed tone signal is to be supplied externally, install shorting jumper E3 in the

EXT position (shorting pins 2 and 3).

3.9.3.4 Keyer Fault Inhibit: If it is desired that a keyer fault inhibit the keyed tone, install shorting jumper E4 in the

ENBL position (shorting pins 1 and

2). If it is desired to continue producing the keyed tone output when a keyer fault occurs, install shorting jumper E4 in the

DSBL position (shorting pins 2 and

3).

3.9.4 POWER TRANSFORMERS A7T1 and A8T1 PRIMARY TAP SELECTION (see figure

MD-24): Connect the primary winding taps of power transformers A7T1 and A8T1 as follows:

(a) Refer to table 3-2 and determine which primary

winding taps of transformer A7T1 should be connected for the mean RMS voltage of the ac power source (previously determined in paragraph 3.7.5).

(b) Gain access to power transformer A7T1's

primary winding taps. Transformer is located on inner front portion of module with its taps facing the module's front panel.

wires identified in table 3-6. Wires #5 (grey) and #6 (grey) are located on the inner section of the front panel of the power supply module.

(d) Connect wires, located in step (c), to the

primary winding taps of power transformer A7T1's, as identified in table 3-2 and depicted in figure MD-24.

(e) Ensure all hardware securing electrical

connections is firmly tightened.

(f) Repeat steps (a) through (e) for power

transformer A8T1, noting that the primary winding taps selected for power transformer A8T1 should be the same as the primary winding taps selected for power transformer A7T1.

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Table 3-3 Selecting Frequency Band Links on Harmonic Filter A12

FREQUENCY PARALLEL SERIES PARALLEL BAND (kHz) SERIES INDUCTORS CAPACITORS CAPACITORS INDUCTORS (C1/C2/C3/C4) (C5/C6/C7/C8) FROM TO L3-1 L4-1 (QUANTITY) (QUANTITY)

190.0 198.4 L1-6 to L2-6 L4-6 L3-6 4 4

198.4 216.2 L1-5 to L2-6 L4-6 L3-5 4 4

216.2 233.9 L1-5 to L2-5 L4-5 L3-5 4 4

233.9 251.2 L1-4 to L2-5 L4-5 L3-4 4 4

251.2 269.9 L1-4 to L2-4 L4-4 L3-4 4 4

269.9 289.9 L1-4 to L2-5 L4-5 L3-4 3 3

289.9 316.1 L1-4 to L2-4 L4-4 L3-4 3 3

316.1 349.7 L1-3 to L2-4 L4-4 L3-3 3 3

349.7 386.9 L1-4 to L2-4 L4-4 L3-4 2 2

386.9 428.1 L1-3 to L2-4 L4-4 L3-3 2 2

428.1 470.1 L1-3 to L2-3 L4-3 L3-3 2 2

470.1 512.4 L1-2 to L2-3 L4-3 L3-2 2 2

512.4 535.0 L1-2 to L2-2 L4-2 L3-2 2 2

3.9.5 HARMONIC FILTER PREINSTALLATION: Complete the pre-installation

procedures on harmonic filter assembly A9 as follows (refer to figure SD-12 to locate harmonic filter assembly A9 and to figures MD-30 through MD-33 for its assembly detail):

The number of in-circuit capacitors is determined by the position of selector plates E1 and E2. Refer to table 3-3 to determine number of in-circuit capacitors for a specific frequency and to figure 3-1 for examples of selector plate positioning. A minimum of two capacitors will be linked by E1 and by E2. All

NOTE

selected capacitors are the same value; therefore, it does not matter which groupings are selected.

Ensure all attaching hardware on capacitor selector plates A9E1/A9E2, taps on inductors A9L1 through A9L4 and the harmonic filter's cover is securely fastened when the requirements of paragraph 3.9.5 have been completed. Failure to do so may result in a hazardous condition or unreliable adjustment.

(a) Gain access to rear panel of harmonic filter

assembly A9 by opening rear hinged door of transmitter cabinet.

Tap selection of series inductors L1 and L2 and parallel inductors L3 and L4 is frequency dependent. Refer to table 3-3 to determine tap connections for a specific frequency. Refer to the electrical schematic depicted in Figure SD-12 as an aid to understanding the function of the band links in harmonic filter A9.

frequency and determine the following:

(b) Remove rear cover from the filter assembly be

removing ten screws and ten washers.

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500 WATT RADIOBEACON TRANSMITTER ND2000A-02X-xx0

- From the Series Inductor column of table 3-3,

determine the taps of inductors A9L1 and A9L2 that are to be interconnected.

- From the Parallel Inductor column of table 3-3,

determine the tap of L4 that is to be connected to L3-1 and the tap of L3 that is to be connected to L4-1.

- From the Series Capacitors column of table 3-3,

determine the number of capacitors that are to be placed in-circuit by capacitor selector plate E1.

- From the Parallel Capacitors column of table 3-

4, determine the number of capacitors that are to be placed in-circuit by capacitor selector plate E2.

(d) Interconnect the taps of series inductors L1 and

L2 as identified in step (c).

(e) Interconnect the taps of parallel inductors L3

and L4 as identified in step (c).

(f) Position series capacitor selector plate E1 over

capacitors C1, C2, C3 and C4 so it places, incircuit, the number of capacitors identified in step (c).

Change position of capacitor selector plates by removing any screws attaching plate to a capacitor, loosen nut in centre of plate and then carefully rotate plate to the desired orientation. An insulating pad is located directly under selector plates E1 and E2. Ensure pad is correctly positioned and then secure plate to each in-circuit capacitor. Tighten bolt in centre of selector plate.

(g) Position parallel capacitor selector plate E2 over

capacitors C5, C6, C7 and C8 so it places, in circuit, the number of capacitors identified in step (c).

(h) Reinstall rear panel on harmonic filter assembly

removed in step (b). Ensure hardware is fastened securely.

Figure 3-1 Positioning of Selector Plates E1 and E2

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INSTALLATION PROCEDURES

3.10 The following procedures must be

performed while installing the transmitter:

3.10.1 TRANSMITTER MODULE INSTALLATION: Install the modulator/power

amplifier modules, power supply modules and exciter modules as follows:

3.10.1.1 Power Supply Modules A7/A8 (see figures MD-1 and MD-23): Install power supply modules A7/A8 as follows:

(a) Verify the pre-installation requirements of

paragraph 3.9 have been completed.

(b) Verify screws securing modulator assemblies

A1, A3, A5, A7 and power amplifier assemblies A2, A4, A5, A6 to terminals 1, 2 and 3 of terminal blocks TB1 through TB8 are firmly tightened.

their respective supports at the front of the transmitter cabinet.

(d) Carefully lift power supply modules and slide

into cabinet.

(e) Connect cableform floating connector P2 to

connector A7J1.

(f) Connect cableform floating connector P3 to

connector A8J1.

(g) Firmly secure attaching hardware to retaining

bolt on rear of module A7.

(h) Firmly secure attaching hardware to retaining

bolt on rear of module A8.

(i) Install 1-inch blanking plugs, provided as

ancillary parts into unused cable entry holes.

3.10.1.2 Modulator/Power Amplifier Modules (see figures MD-1 and MD-4): Install RF power modules A2/A3 as follows:

(a) Verify the pre-installation requirements of

paragraph 3.9 have been completed.

(b) Locate modulator/power amplifier module tray

openings on the front of the transmitter cabinet.

modules into their respective trays.

(d) Firmly secure attaching hardware to retaining

bolt on rear of modules.

(e) Mate BNC coaxial connector P9, which

terminates coaxial cable from exciter module A4, with BNC coaxial connector J2 of modulator/power amplifier module A2.

(f) Mate connector P10, which terminates a

cableform flying lead, with connector J1 of modulator/power amplifier module A2.

(g) Mate connector P11, which terminates a

cableform flying lead, with connector J1 of modulator/power amplifier module A3.

(h) Mate BNC coaxial connector P12, which

terminates coaxial cable from exciter module A5, with BNC coaxial connector J2 of modulator/power amplifier module A3.

3.10.1.3 Exciter Modules (see figures MD-1 and MD-13): Install exciter modules A4/A5 as follows:

(a) Verify the pre-installation requirements of

paragraph 3.9 have been completed.

(b) Locate exciter module tray openings on the

front of the transmitter cabinet.

respective trays.

(d) Do not secure attaching hardware to retaining

bolt on rear of modules at this time.

(e) Mate connector P5, which terminates a

cableform flying lead, with connector J2 of exciter module A4.

(f) Mate connector P6, which terminates a

cableform flying lead, with connector J1 of exciter module A4.

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500 WATT RADIOBEACON TRANSMITTER ND2000A-02X-xx0

(g) Mate connector P7, which terminates a

cableform flying lead, with connector J2 of exciter module A5.

(h) Mate connector P8, which terminates a

cableform flying lead, with connector J1 of exciter module A5.

(i) Mate BNC coaxial connector P19, which

terminates coaxial cable from modulator/ power amplifier module A2, with BNC coaxial connector A4J2 of exciter module A4.

(j) Mate BNC coaxial connector P20, which

terminates coaxial cable from modulator/ power amplifier module A2, with BNC coaxial connector A4J2 of exciter module A5.

3.10.2 EXTERNAL INPUT/OUTPUT INTERFACE CONNECTIONS: Connect the

external input/output wiring to the transmitter as depicted in figure 3-2, observing the following: See figure MD-1 to locate the terminal boards and to figure MD-29 for additional detail.

NOTE

The external control/monitoring cable must be strainrelieved by clamping at cabinet entrance, using a suitable cable clamp. Install blanking plugs in all unused cable entry holes.

(a) Route the external input/output interface

cable(s), through the most appropriate cable entry hole (top of cabinet), through the appropriate ferrite ring(s) and terminate on their respective terminals on interface panel barrier strips TB3 and TB4, (barrier strips TB3/TB4 are accessible through the rear section of the transmitter cabinet).

(b) Using figure 3-2 to determine the final

destination of each conductor, cut each conductor to its required length.

from the end of each conductor. Terminate each conductor with an appropriate terminal lug for a #6 screw.

(d) Connect the input/output conductors to the

appropriate terminals of barrier strips TB3 and TB4 using figure 3-2 as a guide.

3.10.3 RF OUTPUT CABLE CONNECTION: Install the RF output coaxial cable as follows:

(a) Route the RF output coaxial cable to type N

coaxial connector J1, which is located on the top cover of the transmitter cabinet.

(b) Cut the RF output coaxial cable to the required

length. Install a type N coaxial connector on the cable and connect the coaxial cable to RF output connector J1.

3.10.4 LIGHTNING/SAFETY GROUND CONNECTION: Connect a continuous, insulated 4

AWG copper wire or one-inch copper braid, from the station lightning/safety ground system, directly to the safety ground connection at the top of the transmitter. Ensure the conductor wire does not contact any other metal surface of the chassis or cabinet.

3.10.5 AC AND DC POWER CONNECTION

(see figure MD-38): Connect the ac power cabling, and if applicable, the dc power cabling as follows:

NOTE

The ac and dc power source cables must be strainrelieved by clamping at cabinet entrance, using appropriate cable clamps.

(a) Switch off transmitter's ac power source at

service entrance.

(b) Remove appropriate (smaller) knockout from

lower, right-hand, cable-entry.

kit in cable-entry hole.

(d) Route wiring from ac power source through

cable clamp, installed in step (c), to vicinity of barrier strip TB1.

(e) Connect ac power source conductors to barrier

strip TB1 as follows:

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500 WATT RADIOBEACON TRANSMITTER ND2000A-02X-xx0

North American Type Supply 230 VAC (line-to-line)

TB1-1 Line A (115 V ac) TB1-2 Line B (115 V ac) TB1-3 Neutral (Not Connected) TB1-4 Ground

European Type Supply 230 VAC (line-to-neutral)

TB1-1 Line (230 V ac) TB1-2 Neutral TB1-3 No Connection TB1-4 Ground

(f) Remove appropriate (smaller) knockout from

lower, left-hand, cable-entry hole.

(g) Install cable clamp provided in ancillary parts

kit in cable-entry hole.

(h) Route wiring from dc power source through

cable clamp, installed in step (g), to vicinity of barrier strip TB2.

(i) Connect dc power source conductors to barrier

strip TB2 as follows:

- Positive conductor to TB2-1

- Negative conductor to TB2-2

(j) Firmly tighten cable clamps, ensuring wiring is

not pinched.

FIRST STAGE (INITIAL START-UP)

3.11 The first stage of the initial start-up is to

perform a visual inspection and then perform a complete functional test/adjustment procedure as detailed in paragraph 5.3. On completion of the functional test/adjustment procedures, perform the second stage procedures as detailed in paragraph 3.12.

NOTE

The transmitter was fully tested during manufacture and subjected to an extensive burn-in period.

SECOND STAGE (INITIAL START-UP)

3.12 The second stage of initial start-up is to

connect the transmitter's output to its antenna system, interfaced by a suitable antenna tuning arrangement and to adjust the antenna tuning unit in accordance with the instructions in its instruction manual. The transmitter is used as the 50-ohm, RF signal source and the following should be observed:

WARNING

Do not turn on transmitter until requested to do so by personnel at the antenna site. Extremely high, potentially lethal, RF voltages are present in antenna tuning unit when an RF signal of any level is being applied.

(a) Verify the requirements of paragraph 3.11 have

been satisfactorily completed.

(b) Set switches to positions tabulated for Test

Setting in table 4-1.

suitable antenna tuning arrangement, to RF output coaxial connector J1, using a suitable 50 ohm coaxial cable.

(d) Set or verify

O/P POWER potentiometer

A4A2R48 is set fully counter clockwise.

(e) Set the

TEST-Power/Mod switch to FWD PWR.

(f) When requested by personnel at antenna tuning

unit site, set

POWER potentiometer A4A2R48 clockwise for

an initial

TEST-Power/Mod meter.

RF switch to ON and adjust O/P

FWD PWR indication of 25 watts on the

(g) Continuously monitor the forward power

indication on the adjust

O/P POWER potentiometer A4A2R48

TEST-Power/Mod meter and

(side A) to control the RF output level during adjustment of the antenna tuning unit as requested by personnel at the antenna tuning unit site. Do not permit the forward power indication on the

TEST-Power/Mod meter to

exceed 500 watts (the maximum rated carrier power of the transmitter).

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500 WATT RADIOBEACON TRANSMITTER ND2000A-02X-xx0

(h) Adjust or verify antenna tuning unit is adjusted

(by personnel at antenna tuning unit site) in accordance with instructions in the ATU instruction manual.

(i) On completion of antenna tuning unit

adjustment, set the

REFL PWR and verify the reflected power

indication on the

TEST-Power/Mod switch to

TEST-Power/Mod meter is less

than five percent of the forward power reading (25 watts maximum).

(j) Repeat procedures detailed in paragraph 3.12

for the standby (side B) side of the subject transmitter.

THIRD STAGE (INITIAL START-UP)

3.13 The third stage of initial start-up is to

establish the RF output level (intended carrier level) that will provide the desired field strength at the required distance from the antenna, the correct setting (

CUR or VOLT) of RF MON switch A9A2S1 and the

optimum modulation percentage intended modulation depth for the antenna system in use; by operating a transmitter, that has met the requirements of the first stage of initial start-up (successfully completed the functional test/adjustment procedures detailed in paragraph 5.3), into an antenna system that has met the requirements of the second stage of initial start-up.

If the intended carrier level is less than 500 watts, it will be necessary to adjust the carrier level fault threshold level, while operating into the antenna system, as detailed in paragraph 5.3.15.2.

3.13.2 RF MONITOR SIGNAL SOURCE SELECTION: The source of the RF output

information available on is determined by the setting of A9A2S1. When

CUR, a sample of the RF output current waveform is

provided. When

VOLT, a sample of the RF output voltage waveform is

RF MON switch A9A2S1 is set to

RF MON connector A9A2J3

RF MON switch

provided. The correct setting for this switch is the setting which provides the waveform with the greatest modulation depth (percentage). Once established, the setting of

RF MON switch A9A2S1 should be recorded

in the Established Reference section of table 5-2 and

RF MON switch A9A2S1 should be set to the recorded

setting.

3.13.3 INTENDED MODULATION DEPTH: The intended modulation depth is the optimum modulation depth that can be attained (as close as possible to 95%) with the antenna system in use. Once established, the intended modulation depth should be recorded in the Established Reference section of table 5-2 and should be used in all subsequent test/adjustment procedures.

3.13.1 INTENDED CARRIER LEVEL: The intended carrier level is the unmodulated RF output that will provide the desired field strength at the required distance from the antenna. Once established, the intended carrier level should be recorded in the Established Reference section of table 5-2 and should be used in all subsequent functional test/adjustment procedures. Using procedures detailed in paragraph

5.5.4, adjust when side

O/P POWER potentiometer A4A2R48

A is selected until the desired field strength

at the required distance from the antenna is attained. Ensure the unmodulated RF output does not exceed 500 watts.

When the intended carrier level has been determined, set the

POWER

SELECT MAIN TX switch to B and adjust O/P

potentiometer A5A2R48 for the intended

carrier level.

Reduce modulation percentage immediately if the

CURRENT

lamp turns on. Failure to observe this

precaution may result in excessive current flow in the power amplifier stage and cause failure of solid state devices.

- If

RF CURRENT lamp turns on, the RF stress

current threshold is being exceeded. Reduce mod depth immediately to a level that results in

RF CURRENT lamp turning off.

- If

SWR ALARM lamp turns on, the carrier level

will be cutback and it will not be possible to maintain the intended carrier level. Reduce mod depth until

SWR ALARM lamp turns off.

NOTE

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500 WATT RADIOBEACON TRANSMITTER ND2000A-02X-xx0

NOTE

If the intended modulation depth is less than 95%, it will be necessary to adjust the modulation depth fault threshold level, while operating into the antenna system, as detailed in paragraph 5.3.15.3 and the combined voice/tone (A3E mode) modulation depth as detailed in paragraph 5.3.12.

3.13.3.1 Set RF output's modulation envelope to the intended modulation depth as follows:

(a) Verify the intended carrier level has been

determined as detailed in paragraph 3.13.1 and the transmitter's unmodulated RF output is the intended carrier level.

(b) Verify setting of

RF MON switch A9A2S1 has

been determined as detailed in paragraph 3.13.2 and it is set to the established setting.

table 4-1.

(d) Set

TONE LEVEL potentiometers A4A2R19 and

A5A2R19 fully counter clockwise.

(e) Set the

RF switch to ON.

(f) Set

MOD switch A4S2 (A5S2) to ON.

(g) Monitor oscilloscope waveform and slowly

increase modulation depth by adjusting

potentiometer A4A2R19 clockwise until

LEVEL

95% modulation is attained or the

SWR-ALARM

TONE

lamp turns on or until modulation envelope is excessively distorted.

(h) Set

TONE LEVEL potentiometer to the setting

that will provide 95% modulation or the best compromise of depth and distortion when the

SWR-ALARM lamp is not turned on.

(i) Set

(j) Adjust the

(k) Set the

(l) Record

(m) Set

(n)

(o)

(p) Set

(q) Verify the transmitter's unmodulated RF output

(r) Set

(s) Adjust

(t) Set

(u) Adjust

(v) Set

(w)

(x)

TEST-Power/Mod switch to MOD-SET.

SET 100 % MOD potentiometer for

100% indication on the lower scale of the

Power/Mod

meter.

TEST-Power/Mod switch to MOD-READ.

TEST-Power/Mod meter's lower scale

TEST-

indication as the intended modulation depth in Established References section of table 5-2.

TEST-Power/Mod switch to REFL PWR.

TEST-Power/Mod meter's reflected power

indication shall be less than 50 W.

SWR-ALARM lamp shall be off.

SELECT MAIN TX switch to B.

is the intended carrier level.

TEST-Power/Mod switch to MOD-SET.

SET 100 % MOD potentiometer for 100%

indication on the lower scale of the

Power/Mod meter.

TEST-Power/Mod switch to MOD-READ.

TONE LEVEL potentiometer A5A2R19

TEST-

for modulation depth recorded in step (l).

TEST-Power/Mod switch to REFL PWR.

TEST-Power/Mod meter's reflected power

indication shall be less than 50 W.

SWR-ALARM lamp shall be off.

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500 WATT RADIOBEACON TRANSMITTER ND2000A-02X-xx0

Figure 3-2 External Input/Output Interface

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500 WATT RADIOBEACON TRANSMITTER ND2000A-02x-xx0

SECTION 4

OPERATING INSTRUCTIONS

GENERAL

4.1 This section provides the information

required to place the subject transmitter in operation. Normally, the transmitter will not be attended during use.

EMERGENCY SHUTDOWN PROCEDURE

4.2 There are no special precautions to be

taken if an emergency shutdown is required. Switch off ac power by placing A6S1 to its

OFF position or turn off ac power source

POWER - AC LINE switch

at the service entrance. If a battery is being used as the transmitter's dc power source, set

BATTERY switch A6S2 to its OFF position.

POWER -

CONTROLS AND INDICATORS

4.3 The following paragraphs list assemblies

that contain controls and indicators, identify illustrations that depict their location and markings and reference tables that describe their purpose and function.

4.3.1 CONTROL/MONITOR PANEL CONTROLS AND INDICATORS: Figures MD-2

and MD-3 depict the controls and indicators on control/monitor panel A1. Table 4-2 is keyed to the reference designation assigned to the controls/ indicators and explains their function.

NOTE

TEST-Power/Mod meter's RF Kilowatts scale is a

square law scale. Resulting non-linearity makes it difficult to read less than 100 watts. Any reading that is less than fifty percent of the 100 watt mark is less than 25 watts.

4.3.2 RF POWER MODULE CONTROLS AND INDICATORS: Figures MD-4 thru MD-12

depict the controls and indicators on RF power modules A2/A3 and their associated assemblies. Table 4-3 is keyed to the reference designation assigned to the controls/indicators and explains their function.

4.3.3 EXCITER MODULE CONTROLS AND INDICATORS: Figures MD-13 to MD-21

depict the controls and indicators on exciter modules A4/A5 and their associated printed wiring boards/ assemblies. Table 4-4 is keyed to the reference designation assigned to the controls/indicators and explains their functions.

4.3.4 POWER ON/OFF PANEL CONTROLS AND INDICATORS: Figure MD-22 depicts the

controls and indicators on power on/off panel A6. Table 4-5 is keyed to the reference designation assigned to the controls/indicators and explains their functions.

4.3.5 POWER SUPPLY MODULE CONTROLS AND INDICATORS: Figure MD-23

thru MD-28 depict the controls and indicators on power supply modules A7/A8. Table 4-6 is keyed to the reference designation assigned to the controls/ indicators and explains their function.

4.3.6 HARMONIC FILTER CONTROLS: Figures MD-30 through MD-33 depict the controls of harmonic filter assembly A9. Table 4-7 is keyed to the reference designation assigned each control and explains their function.

4.3.7 MONITOR PWB CONTROLS AND INDICATORS: Figures MD-34 and MD-35 depict

the controls and indicators on the monitor PWB A10. Table 4-8 is keyed to the reference designation assigned to the controls/indicators and explains their function.

4.3.8 BATTERY PANEL CONTROLS AND INDICATORS: Figure MD-36 depicts the controls

and indicators on battery panel assembly A11. Table 4-9 is keyed to the reference designation assigned to the controls/indicators and explains their function.

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4.3.9 MISCELLANEOUS (CABINET/ INTERFACE PANEL) CONTROLS AND INDICATORS: Figure MD-1 depicts the controls on

the transmitter cabinet and figure MD-29 depicts the controls on the interface panel assembly. Table 4-10 is keyed to the reference numbers assigned to the controls and explains their function.

PRESTART-UP CHECKS

4.4 Prior to applying input power to the

transmitter, observe the following:

(a) Verify the pre-installation requirements

described in paragraphs 3.9.1 thru 3.9.5 have been completed.

(b) Verify the transmitter modules have been

properly installed in the cabinet and all panels are installed and securely fastened.

connected as shown in figures SD-1 and SD-2.

(d) Verify the transmitter's RF output connector J1

is terminated into a 50 ohm load.

- An antenna that is interfaced by a tuned antenna

tuning unit for normal adjustment, testing and operating procedures.

- A 50 ohm, resistive, dummy load with a wattage

rating of twice the rated carrier power of the transmitter for harmonic filter procedures and for specified special adjustment.

(e) Verify the voltage of the input power source is

between 180 and 250 (230 nominal) V ac, at the appropriate frequency and power rating for the transmitter (1200 VA).

TURNING ON TRANSMITTER

4.5 Turn on transmitter as described in

paragraph 5.3.2 for initial startup and after repairs that may have affected the adjustment accuracy, at other times, set the switches to position tabulated for Test Setting in table 4-1 initially and then to settings tabulated for Operating Setting.

RESETTING TRANSMITTER

4.6 Transmitters that have been transferred to

the standby side or that have shutdown, may be reset by momentarily switching the transmitter off and then back to on. This action may be taken locally by using the

RF switch or remotely using remote on/off control.

Transmitters that have been reset will always go to the selected main side of the subject transmitter (original state).

MODULATION DEPTH WHEN USING A HIGH 'Q' ANTENNA:

4.7 A typical radiobeacon antenna is relatively

inefficient, since it is very short when compared with the wavelength of the carrier frequency. The high capacitive reactance of a typical antenna is tuned to the carrier frequency, by an antenna tuning unit's (ATU) loading coils, to produce a series resonant circuit. The resulting net antenna system resistance is then transformed to 50 ohms by a matching transformer. When the antenna is very short compared with the wavelength of the carrier frequency, the resonant circuit has an extremely high 'Q'. Under these conditions, the antenna system may present a 50-ohm load to the transmitter at the carrier frequency but a different impedance at the sideband frequencies. The mismatch at the sideband frequencies will cause a standing wave on the feed cable. Depending upon the length of the feed cable, the sideband impedance of the antenna system will appear to be more or less than 50 ohms. When the transmitter is connected to a high 'Q' antenna system, the difference between the carrier impedance and the sideband impedance may cause RF stress current limits to be exceeded, as described in paragraph 4.7.1, or reflected power thresholds to be exceeded, as described in paragraph 4.7.2. When RF stress current limits are exceeded, instant remedial action must be taken.

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4.7.1 RF CURRENT ALARM INDICATION: A current probe in the input to

harmonic filter A9 provides an RF current sample

that is representative of the RF current in the active modulator/power amplifier module. This sample is applied to a logic circuit, is peak detected and causes the

RF CURRENT ALARM lamp to turn on or flash

when stress current thresholds are exceeded. The stress current threshold is established during adjustment, when the transmitter's RF output is being applied to a precision, 50-ohm, resistive dummy load, and the load impedance is precisely 50 ohms at the carrier and sideband frequencies. This threshold represents the peak RF current when the RF carrier's forward power level is 500 watts, the modulation depth is 95 percent and the carrier/sideband impedance is 50 ohms. If this current is exceeded for any reason, the on or flash. When the

RF CURRENT ALARM lamp will turn

RF CURRENT ALARM lamp is

4.7.3 REMEDIAL ACTION IN BEACON MODE: When operating in beacon (no voice) mode,

the modulation depth should be reduced by adjusting

TONE LEVEL potentiometer (R19) counter clockwise

until

RF CURRENT ALARM lamp A1A1DS4 just turns

off. The resultant modulation depth is the maximum obtainable with that particular antenna system.

4.7.4 REMEDIAL ACTION IN VOICE AND BEACON MODE: When operating in voice and

beacon mode, the modulation depth should be reduced by adjusting both (R20) and

VOICE MOD % potentiometer (R21) counter

TONE MOD % potentiometer

clockwise, when tone and voice audio are both present, until

RF CURRENT ALARM lamp A1A1DS4

just turns off. The 35/60 ratio of tone percentage to voice percentage should be maintained when adjustments are completed.

on or flashing, remedial action must be taken by adjusting the appropriate potentiometers on modulator driver PWB boards A4A2 and A5A2.

4.7.2 SWR-ALARM INDICATION: A voltage probe at the output of harmonic filter A9 provides a voltage sample that is representative of the sensed reflected power. This sample is applied to a logic circuit, is peak detected and causes the carrier level to be cutback (reduced) and

SWR-ALARM lamp

to turn on when the peak reflected power exceeds a nominal 115 watts. If there is no reflected power when an unmodulated carrier (CW) is applied to the antenna system, but there is reflected power when the carrier is modulated (MCW), the sideband limitations of the antenna system may dictate a reduction in modulation depth to maintain the carrier level at its intended level. If the

SWR-ALARM lamp is not on

during CW emissions but turns on during MCW emissions, the modulation depth (percentage) is too high for the antenna in use and the carrier level will be cutback when sideband power is causing the

SWR-ALARM lamp is on. If reflected

SWR-ALARM lamp to

turn on, remedial action must be taken by adjusting the appropriate potentiometers on modulator driver printed wiring boards A4A2 and A5A2.

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500 WATT RADIOBEACON TRANSMITTER ND2000A-02x-xx0

Table 4-1 Preliminary Switch Settings

USED IN TEXT DES SETTING SETTING SETTING

NOMENCLATURE REF INITIAL TEST OPERATING

SPEAKER A10S3 OFF OFF OFF MONITOR A1S4 BYPASS BYPASS NORMAL TEST-Volts/Current A1S5 OFF OFF OFF SELECT MAIN TX A1S3 A A A or B RF A1S1 OFF OFF ON TEST-Power/Mod A1S6 OFF OFF OFF CONTROL A1S2 LOCAL LOCAL LOCAL or REMOTE KEYING A4S1 OFF OFF ON KEYING A5S1 OFF OFF ON MOD A4S2 OFF OFF ON MOD A5S2 OFF OFF ON POWER-AC LINE A6S1 OFF ON ON POWER-BATTERY A6S2 OFF OFF ON POWER-AC LINE A7S1 OFF ON ON POWER AC LINE A8S1 OFF ON ON RF MON A9A2S1 VOL or CUR As Determined As Determined

Side 'A' Status A10S2 NORMAL NORMAL NORMAL Side 'B' Status A10S1 NORMAL NORMAL NORMAL

MODULATION PERCENTAGE INDICATION

4.8 Current and voltage transformers in the

forward/reflected power probe, which is in the output of harmonic filter A9, provide samples that are representative of the RF output current and voltage waveforms. When the transmitter's RF output is being applied to a precision, 50-ohm, resistive dummy load and the load impedance is precisely 50 ohms at the carrier and sideband frequencies, the waveforms provided by both transformers will be identical. When the transmitter's RF output is being applied to an antenna system, the sideband impedance will be

high or lower than 50 ohms. If the sideband impedance is less than 50 ohms, the current transformer's waveform is selected as the source for the RF monitor sample. If the sideband impedance is greater than 50 ohms, the voltage transformer's waveform is selected as the source for the RF monitor sample. The RF monitor sample is applied to the

MONITOR

connector for external monitoring and to a

modulation detector circuit. The output of the modulation detector circuit is displayed on the

Power/Mod

meter as a modulation percentage

TEST-

indication.

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Table 4-2 Control/Monitor Panel Controls and Indicators

REF FIG NOMENCLATURE FUNCTION DES NO. USED IN TEXT

PANEL MARKING/

A1A1DS1 MD-2

STANDBY-ALARM

When turned on, indicates the transmitter has switched from the selected main-side to standby-side.

A1A1DS2 MD-2

SWR-ALARM

When turned on, indicates a reflected power in excess of 60 watts has been sensed at the output of the harmonic filter.

When the dc option is not installed, it may indicate the ac power is more than 10% low.

A1A1DS3 MD-2

SHUTDOWN ALARM

Turns on when the transmitter has shut down.

A1A1DS4 MD-2

RF CURRENT ALARM

When turned on, indicates troughs of modulation envelope, as sensed by an RF current probe at the harmonic filter's input are exceeding the preset overmod threshold. Normally turns on when the antenna impedance is less than 50 ohms at the sideband frequency and the antenna current is exceeding the current that would be present if the antenna impedance was 50 ohms.

A1A1DS5 MD-2

BATTERY-ALARM

When turned on, indicates transmitter's B- voltage is being provided by an external dc power source (battery).

A1A1DS6 MD-2

RF ON

When turned on, indicates operating voltage for the subject transmitter is being supplied by the ac power or dc power source.

A1A1DS7 MD-2

CONTROL-REMOTE

Turns on when the CONTROL switch is set to REMOTE and the on/off switching facility has been extended to a remote site.

A1A1DS8 MD-2

MONITOR - BYPASS

When turned on, indicates MONITOR switch is set to

BYPASS and changeover is inhibited.

A1M1 MD-2

TEST-Power/Mod

Displays parameter selected by the TEST-Power/Mod switch. Forward and reflected power readings are obtained from the upper scale. Modulation percentage readings are obtained from the lower scale.

A1M2 MD-2

TEST-Volts/Current

Displays parameter selected by the TEST-Volts/Current switch. Voltage readings are obtained from the upper scale. Current readings are obtained from lower scale.

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Table 4-2 Control/Monitor Panel Controls and Indicators (Continued)

REF FIG NOMENCLATURE FUNCTION DES NO. USED IN TEXT

PANEL MARKING/

A1S1 MD-2

Turns the transmitter ON or OFF. Resets the transmitter to its original state when set to then returned to

ON. (If operating in the standby mode,

OFF and

transmitter will reset to main).

A1S2 MD-2

CONTROL

Extends ON/OFF switching facility to a remote site when set to

REMOTE.

A1S3 MD-2

SELECT MAIN TX

Selects either side A or side B to provide the RF output for the subject transmitter.

A1S4 MD-2

MONITOR

Inhibits changeover circuits when set to BYPASS. Allows maintainer to work on a circuit without concern for the parameters that would normally cause a changeover.

A1S5 MD-2

TEST-Volts/Current

Test switch that selects parameter, DC CURRENT +15V,

-15V, +24V or B-V for the main or standby transmitter to

be displayed on movement when set to

TEST meter M2. Shorts out meter

OFF.

A1S6 MD-2

TEST-Power/Mod

Test switch that selects parameter FWD PWR, MOD SET,

REFL PWR or MOD READ to be displayed on TEST

meter M1. Shorts out meter movement when set to

OFF

A1A1R2 MD-3

Meter Cal

Adjusted for a precise B- V dc indication on TEST meter A1M2 during test/adjustment procedures.

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Table 4-3 Modulator/Power Amplifier Module Controls and Indicators

REF FIG NOMENCLATURE FUNCTION DES NO. USED IN TEXT

PANEL MARKING/

*A9DS1 MD-4

B-

Indicates the B- voltage is being applied when on.

*A9DS2 MD-4

PA VOLTS - 4

Indicates modulator *A7 is functioning and is applying a modulated B- voltage to power amplifier *A8 when on.

*A9DS3 MD-4

PA VOLTS - 3

Indicates modulator *A5 is functioning and is applying a modulated B- voltage to power amplifier *A6 when on.

*A9DS4 MD-4

PA VOLTS - 2

Indicates modulator *A3 is functioning and is applying a modulated B- voltage to power amplifier *A4 when on.

*A9DS5 MD-4

PA VOLTS - 1

Indicates modulator *A1 is functioning and is applying a modulated B- voltage to power amplifier *A2 when on.

*F1 MD-9

7A SLOW

Fuses B- voltage to modulator *A1 at 7.0 amperes.

*F2 MD-9

7A SLOW

Fuses B- voltage to modulator *A3 at 7.0 amperes.

*F3 MD-9

7A SLOW

Fuses B- voltage to modulator *A5 at 7.0 amperes.

*F4 MD-9

7A SLOW

Fuses B- voltage to modulator *A7 at 7.0 amperes.

*S1 MD-5

Thermal

Normally closed thermal switch. Opens and removes PWM from the associated modulators when temperature exceeds 82°C.

TP1 MD-4

PA VOLTS

Provides a test point to monitor the average output voltage (modulated B- V dc) from the modulators.

* Denotes partial reference designation shown. For complete reference designation, prefix with A2

or A3 as appropriate.

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Table 4-4 Exciter Module Controls and Indicators

REF FIG NOMENCLATURE FUNCTION DES NO. USED IN TEXT

PANEL MARKING/

A1DS1 MD-17

KEYER FAULT

Indicates a problem has occurred with one or both EEPROMs on the keyer PWB. Action taken on the transmitter is dependent on the setting of the

ENBL/DSBL jumper (E4).

A1E1/ A1E2

MD-17

400/1020

Shunt posts that determine the keyed tone frequency of the keyer PWB

Installed to short pins 1 and 2 for 1020 Hz. Installed to short pins 2 and 3 for 400 Hz.

A1E3 MD-17

INT/EXT

Shunt post that determines the keyed tone source

A1E4 MD-17

A1S1

MD-17

A1S4

A1U11

MD-17

A1U14

ENBL/DSBL

Keyer Setup Switches

Keyer Content Display

Installed in

INT position (shorting pins 1 and 2) for an

internal tone oscillator. Installed in

EXT position (shorting pins 2 and 3) for an

external oscillator..

Shunt post that determines the action taken when a keyer fault occurs.

When installed in the

ENBL position (shorting pins 1

and 2), the fault inhibits the keyed tone output. A continuous tone will be generated when this occurs.

When installed in the DSBL: position (shorting pins 2 and 3), the fault, although indicated by

KEYER FAULT

lamp DS1, has no effect on the keyed tone output.

Pushbutton switches S1 (up), S2 (left), S3 (right) and S4 (down), and alphanumeric displays U11 through U14, are used to configure the keyer’s contents (type, characters, standby ‘1’ code, frame type and frame length). Pressing S2 and S3 simultaneously enters the setup menu. This menu is used to set up all aspects of the keyer. To navigate the setup menu, S1 increments, S4 decrements, S2 backs up,, and S3 accepts and proceeds to the next selection.

Alphanumeric displays that, during normal operation, indicate the keyed characters (after setup, display inactive until a pushbutton switch is pressed). In conjunction with switches S1 through S4, the displays are used to set up/change the keyer contents. When all characters display a ‘!’ character, a fault exists with the keyer PWB’s EEPROM(s).

Page 4-8 15 January 2005

500 WATT RADIOBEACON TRANSMITTER ND2000A-02x-xx0

Table 4-4 Exciter Module Controls and Indicators (Continued)

REF FIG NOMENCLATURE FUNCTION DES NO. USED IN TEXT

PANEL MARKING/

A2C22 MD-18

PWM Freq

Adjusted to set the frequency of the PWM squarewave (ramp) generator to the optimum frequency (nominally 70kHz) for the assigned carrier frequency.

A2R2 MD-18

VOICE LEVEL

Adjusts audio level to the voice modulation amplifier.

A2R19 MD-18

TONE LEVEL

Adjusted to set the amplitude of the tone signal to the level that will provide the desired modulation percentage when operating in keyed or continuous MCW mode (press-to-talk input not being applied).

A2R20 MD-18

TONE MOD %

Adjusted to set the amplitude of the tone signal to the level that will provide the desired modulation percentage when a press-to-talk input is being applied (normally 35% of modulation percentage present when press-to-talk input is being applied).

A2R21 MD-18

VOICE MOD %

Adjusted to set the amplitude of the voice audio to the level that will provide the desired modulation percentage when a press-to-talk input is being applied (normally 60% of modulation percentage present when press-to-talk input is being applied).

A2R48 MD-18

O/P POWER

Adjusted to set the on/off ratio of the mod drive to the ratio that will produce the desired RF output power level .

A2R58 MD-18

RAMP ADJ

Adjusted for the reference voltage that will position the negative going peaks of PWM ramp integrator's triangular waveform output, measured at TP5, at zero volts dc (ground).

#A3E1/E2/ E4

MD-♦

RF Drive Internal/External

Shunt posts that select the source of the RF drive signal. Refer to the RF synthesizer PWB’s service instruction manual for further detail.

#A3E3

MD-♦

PDM Selection

Not used in NDB transmitters.

#A3E5

MD-♦

Balanced Drive Matching

7-position shunt post that allows matching of the balanced drive signal.

Set to E5:A for NDB

transmitters.

#A3R32

MD-♦

SYMMETRY

Not used in NDB transmitters.

Page 4-9 15 January 2005

500 WATT RADIOBEACON TRANSMITTER ND2000A-02x-xx0

Table 4-4 Exciter Module Controls and Indicators (Continued)

REF FIG NOMENCLATURE FUNCTION DES NO. USED IN TEXT

PANEL MARKING/

#A3R41

MD-♦

IPM BAL

Not used in NDB transmitters .

#A3S1

MD-♦

X 1000

Rotary 10-position BCD switch that selects the carrier frequency’s thousands digit (either ‘0’ or ‘1’), in kHz.

#A3S2

MD-♦

X 100

Rotary 10-position BCD switch that selects the carrier frequency’s hundreds digit, in kHz.

#A3S3

MD-♦

X 10

Rotary 10-position BCD switch that selects the carrier frequency’s tens digit, in kHz.

#A3S4

MD-♦

X 1

Rotary 10-position BCD switch that selects the carrier frequency’s units digit, in kHz.

#A3S5

MD-♦

X 0.1

Rotary 10-position BCD switch that selects the carrier frequency’s tenths digit, in kHz.

#A3S6:1/2/

MD-♦

IPM Correction Capacitance

#A3S6:4

MD-♦

*A3C10 MD-19

*A3- MD-19

DS1 MD-13

IPM Correction Enable/Disable

Osc Freq

Freq Divider Links

'A' to 'B' Link

'C' to 'D' Link

'E' to 'F' Link

AUDIO LIMITER

Not used in NDB transmitters.

Set to closed (disabled) for NDB transmitters.

Adjusted to fine tune the carrier oscillator to the frequency that will provide the desired RF carrier frequency.

Connects PWB pad 'E' to appropriate output of frequency divider (4, 8 or 16). Refer to paragraph

3.9.2.1 for interconnection information.

Installed when crystal oscillator provides the RF carrier frequency of the transmitter ('C' to 'D' link not installed).

Not Used

Indicates amplitude of input voice audio is exceeding the preset threshold level that represents the maximum desired modulation depth and the voice audio is being attenuated to this level when on.

Page 4-10 15 January 2005

500 WATT RADIOBEACON TRANSMITTER ND2000A-02x-xx0

Table 4-4 Exciter Module Controls and Indicators (Continued)

REF FIG NOMENCLATURE FUNCTION DES NO. USED IN TEXT

PANEL MARKING/

DS2 MD-13

RF DRIVE ALARM

Indicates the RF drive level has fallen below the minimum RF drive threshold when on.

DS3 MD-13

MOD DRIVE ALARM

Indicates the on/off radio of the mod drive signal's variable pulse width is incorrect and the mod drive output is being inhibited when on.

F1 MD-16

1A SLOW

Fuses B- voltage to exciter assembly at 1.0 ampere.

R5 MD-13

PWR TRIM-LOCAL

Provides a local adjustment to reduce the carrier level while maintaining the modulation percentage during testing. Normally set fully clockwise.

*S1 MD-13

KEYING

Determines status of associated keyer PWB. Keying is inhibited when set to

OFF.

S2 MD-13

MOD

Determines status of associated modulator driver PWB's modulating audio. The modulating audio is inhibited when set to

OFF.

Partial reference designation shown. For complete reference designation, prefix with A4 or A5

as appropriate. Refer to Figure MD-14 to locate A1 and A3 and to Figure MD-15 to locate A2 and A4.

# - Denotes used only when RF synthesizer PWB is installed as A3. * - Denotes used only when RF (crystal) oscillator is installed as A3. ♦ - Refer to the RF synthesizer PWB’s service instruction manual to locate referenced item.

Page 4-11 15 January 2005

500 WATT RADIOBEACON TRANSMITTER ND2000A-02x-xx0

Table 4-5 Power On/Off Panel Controls and Indicators

REF FIG NOMENCLATURE FUNCTION DES NO. USED IN TEXT

PANEL MARKING/

A6DS1 MD-22

Power - Ac Line

Indicates ac voltage present at power supply modules A7 and A8.

A6F1 MD-22

BATTERY

Fuses the transmitter's external dc power source (battery) at 30 amperes.

A6S1 MD-22

POWER-AC LINE

Switches the ac power source being supplied to power supply modules A7 and A8

ON or OFF.

A6S2 MD-22

POWER-BATTERY

Switches the external dc power source being supplied to the optional battery panel A11

ON or OFF.

Page 4-12 15 January 2005

500 WATT RADIOBEACON TRANSMITTER ND2000A-02x-xx0

Table 4-6 Power Supply Module Controls and Indicators

REF FIG NOMENCLATURE FUNCTION DES NO. USED IN TEXT

PANEL MARKING/

*DS1 MD-23

CONVERTER-+24V

Indicates B- V dc to +24 V dc converter is providing 24 V dc when on.

*DS2 MD-23

POWER-DC SUPPLY

Indicates the B- voltage is present when on.

*F1 MD-23

CONVERTER

Fuses B- dc voltage being applied to B- V dc to +24 V dc converter at 1.0 amperes.

*F2 MD-23

POWER-AC LINE

Fuses line side of the 230 V ac power being applied to the power transformer (line A when ac power source is North American style split phase) at 30 amperes.

*F3 MD-23

POWER-AC LINE

Fuses line B side of the 230 V ac power being applied to the power transformer (when ac power source is North American style split phase) at 30 amperes. Bypassed when ac power source is European style (line-neutral).

*S1 MD-23

POWER-AC LINE

Switches the ac power source, being applied to the power transformer within the power supply module,

ON or OFF when POWER-AC LINE switch A6S1 is set

ON.

*A1R12 MD-26

B-Level

Adjusted to set the B- V dc output of the associated power supply to precisely -50 V dc.

*A2A1R10 MD-27A

+24 VDC Level

Adjusted to set the 24 V dc output of the associated power supply's B- V dc to +24 V dc converter to precisely +24.0 V dc.

*A3R3 MD-27B

Low AC Voltage Threshold

Adjusted to provide a Battery-Alarm lamp indication when the ac power source decreases by fifteen percent.

*TP1 MD-25

B- Volts

Provides a test point to monitor the B- V dc from associated power supply (-50 V dc).

* Denotes partial reference designation shown. For complete reference designation, prefix with A7 or

A8 as appropriate.

Refer to Figure MD-24 to locate A2 and to Figure MD-25 to locate A1 and A3.

Page 4-13 15 January 2005

500 WATT RADIOBEACON TRANSMITTER ND2000A-02x-xx0

Table 4-7 Harmonic Filter Assembly Controls and Indicators

REF FIG NOMENCLATURE FUNCTION DES NO. USED IN TEXT

PANEL MARKING/

A9A2S1 MD-29

RF MON

Determines the source of the RF output waveform for

TEST meter M1's modulation readings and for the

monitoring sample provided at the

RF MONITOR output

connector. Sample provided by current transformer A9A2T3 is the source when

CUR is selected. Sample

provided by voltage transformer A9A2T1 is the source when

VOLT is selected.

A9E1 MD-30

Capacitor Selector Plate

Determines the number of in-circuit capacitors in the output filter's series tuned L/C circuit. Orientation permits selection of 2, 3 or 4 capacitors. Refer to figure 3-2 for examples.

A9E2 MD-30

Capacitor Selector Plate

Determines the number of in-circuit capacitors in the output filter's parallel tuned L/C circuit. Orientation permits selection of 2, 3 or 4 capacitor. Refer to Figure 3-2 for examples.

Page 4-14 15 January 2005

500 WATT RADIOBEACON TRANSMITTER ND2000A-02x-xx0

Table 4-8 Monitor PWB Controls and Indicators

REF FIG NOMENCLATURE FUNCTION DES NO. USED IN TEXT

PANEL MARKING/

A10DS1 MD-34

A10LS1 MD-34

A10R7 MD-34

A10R18 MD-34

A10R23 MD-34

A10R48 MD-34

A10R79 MD-34

A10R95 MD-34

SWR CUTBACK THRESHOLD

SET THRSH

SPEAKER

MOD THRSH

CARR THRSH

RF CURRENT

CHANGEOVER DELAY

FWD PWR CAL

Flashes between tone periods during keyed MCW operation. Continuously on when RF carrier level falls below preset carrier fault threshold (normally -3.0 dB) or when modulation level falls below preset modulation fault threshold (normally -4.0 dB) or keying fails.

Provides an audible signal for local monitoring of the detected modulation.

Adjusted to produce a modulation fault signal when modulation level falls below the desired percentage (must be at least 1.0 dB below the carrier fault threshold). Ultimately will cause the transmitter to shut down if the modulation percentage does not exceed this minimum threshold level within the time delay period of the shutdown circuit.

Adjusted to produce a carrier fault signal when the carrier level falls below the desired level (usually -3.0 dB). Ultimately will cause transmitter shut down if the carrier level does not exceed this minimum threshold level within the time delay period of the shutdown circuit.

Adjusted, when operating into a 50.0 ohm resistive load, for a modulation threshold (normally 95%) that represents the maximum permissible before peak RF current thresholds are exceeded. When the modulation envelope exceeds 95%, the peak detected RF current sample will cause the

RF CURRENT ALARM lamp to

turn on.

Adjusted for a delay of between 20 and 80 seconds before transmitter changeover/shutdown occurs.

Adjusted, during adjustment procedures, to precisely set the forward power indication on the when the

TEST switch is set to FWD PWR.

TEST meter,

Adjusted for SWR fault threshold that represents the maximum acceptable reflected power before an cutback output will be produced. When an

SWR SWR

cutback output is produced, the RF output will be cutback to a level that will ensure the reflected power does not exceed the threshold level.

Page 4-15 15 January 2005

500 WATT RADIOBEACON TRANSMITTER ND2000A-02x-xx0

Table 4-8 Monitor PWB Controls and Indicators (Continued)

REF FIG NOMENCLATURE FUNCTION DES NO. USED IN TEXT

PANEL MARKING/

A10R107 MD-34

REFL PWR CAL

Adjusted to precisely set the reflected power indication on the

REFL PWR, during test/adjustment.

TEST meter, when the TEST switch is set to

A10R114 MD-34

SET 100 % MOD

Adjusted for 100 % modulation indication on the TEST meter when

TEST switch S6 is set to MOD-SET and

transmitter is operating in CW mode.

A10R115 MD-34

SPEAKER VOLUME

Adjusts the loudness output of SPEAKER LS1.

A10F1 MD-34

Monitor B-V

Fuses the B- voltage to monitor PWB A10.

A10S1 MD-34

Side 'B' Test

When set to TEST, inhibits the RF input to the harmonic filter assembly and enables the user to perform adjustment/repair procedures on the (side

B will be operating into an open circuit).

B side

A10S2 MD-34

Side 'A' Test

When set to TEST, inhibits the RF input to the harmonic filter assembly and enables the user to perform adjustment/repair procedures on the (side

A will be operating into an open circuit).

A side

A10S3 MD-34

SPEAKER

Switches an audible signal to SPEAKER LS1 for local monitoring of the detected modulation.

Do not change setting of Side A Test switch or Side B Test switch when transmitter

is turned on. Always set

RF switch to OFF before changing settings.

Page 4-16 15 January 2005

500 WATT RADIOBEACON TRANSMITTER ND2000A-02x-xx0

Table 4-9 Battery Panel Controls and Indicators

REF FIG NOMENCLATURE FUNCTION DES NO. USED IN TEXT

PANEL MARKING/

A11S1 MD-36

BATTERY RESET

Resets transmitter's low battery voltage shutdown circuit, utilizing a slow charge circuit, when discharged batteries are replaced by charged batteries. Used only when ac power is not being applied.

A11A1R7 MD-36

Side 'A'-Low Battery Threshold

Adjusted during special test to set the Low Battery Threshold to the desired level for side A of the

transmitter (set when dc power source is a nominal -42 V dc)..

A11A1R8 MD-36

Side 'B'-Low Battery Threshold

Adjusted during special test to set the Low Battery Threshold to the desired level for side B of the

transmitter (set when dc power source is a nominal -42 V dc).

Page 4-17 15 January 2005

500 WATT RADIOBEACON TRANSMITTER ND2000A-02x-xx0

Table 4-10 Miscellaneous (Cabinet/Interface Panel) Controls and Indicators

REF FIG NOMENCLATURE FUNCTION DES NO. USED IN TEXT

PANEL MARKING/

F1 MD-29 0.25A Fuses B- V dc (A) applied to TB4-8, for external

monitoring, at 0.25 amperes.

F2 MD-29 0.25A Fuses B- V dc (B) applied to TB4-9, for external

monitoring, at 0.25 amperes.

F3 MD-29 3.0A Fuses B- V dc (A) input to monitor/interface panel

A10, exciter A4, control/monitor panel A1 and battery panel A11 (optional).

F4 MD-29 0.25A Fuses +15 volt dc output from monitor/interface panel

A10.

F5 MD-29 0.25A Fuses +24 V dc output from monitor/interface panel

A10.

F6 MD-29 3.0A Fuses B- V dc (B) input to monitor/interface panel

A10, exciter A4, control/monitor panel A1 and battery panel A11 (optional).

R2 MD-1

Current 'A' Cal

Adjusted for DC CURRENT (A) indication on the TEST meter that is representative of the current being consumed by transmitter side

R3 MD-1

Current 'B' Cal

Adjusted for DC CURRENT (B) indication on the TEST meter that is representative of the current being consumed by transmitter side

Page 4-18 15 January 2005

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

SECTION 5

TESTING AND ADJUSTMENTS

GENERAL

5.1 This section contains adjustment

procedures that are performed in conjunction with functional tests. Special and operational adjustments procedures are also included in this section.

NOTE

Instructions are presented in a step-by-step format. It is recommended that personnel who are not familiar with detailed circuit theory or do not realize what impact a specific adjustment will have on other steps, follow instructions in the order presented. It is recommended instructions be followed sequentially during initial start-up and after major repairs.

OPERATION OF EQUIPMENT

5.2 Observe the instructions presented in

section 4 when turning the system on or off. Detailed control and indicator information is presented in tables 4-2 through 4-10.

NOTE

TEST-Power/Mod meter's forward/reflected power

scale is a square law scale. Resulting non-linearity makes it difficult to read less than 50 watts. Any reading that is less than fifty percent of the 50 watt mark is less than 12.5 watts.

The carrier portion of the RF output is referred to as the intended carrier level in the following procedures. This level is normally determined by flight/range tests during initial installation (refer to paragraph 3.13). The intended carrier level must not exceed 500 watts or be less than 100 watts. Once established, the RF output power that provides the desired field strength at the specified range shall be used as the intended carrier level. Use 500 watts as the intended carrier level if flight/range tests have not been completed.

The depth of the modulation envelope is referred to as the intended modulation depth in the following. The modulation depth is normally dictated by the 'Q' of the antenna system and is determined during initial installation (refer to paragraphs 4.7 and 3.13). The intended modulation depth should be as close to 95 percent as is possible. Once determined, the optimum modulation percentage that can be attained from a specific transmitter/antenna system shall be used as the intended modulation depth. Use ninety-five percent as the intended modulation depth, if no other value has been established.

TEST/ADJUSTMENT PROCEDURES

5.3 Functional test/adjustment procedures shall

be performed and the results recorded for comparison with past and future test results, as a routine part of scheduled maintenance checks and as the first step in troubleshooting procedures. The adjustment procedures, performed in conjunction with the functional tests, consist of adjusting appropriate electrical components to bring specific operating parameters of a fully assembled transmitter into the desired limits. The functional test/adjustment procedures are carried out with the transmitter's RF output connected to a precision, 50 ohm, resistive dummy load.

NOTE

Functional test/adjustment procedures are presented in a sequence that will accommodate a complete functional test and/or alignment of transmitter.

Printed wiring board (PWB) mounted potentiometers are four-turn potentiometers that have a clutch at either extreme of their adjustment. Their wipers must be turned a minimum of four turns in one direction to ensure they have been set fully clockwise or fully counter clockwise.

Page 5-1

15 January 2005

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

5.3.1 TEST/ADJUSTMENT TEST EQUIPMENT: The following test equipment is

required to perform the functional test/adjustment procedures. Refer to table 1-3 for additional information regarding test equipment identification and/or specifications.

- Precision, 50-ohm, resistive, dummy load, rated

at 1000 watts

- Digital multimeter

- Audio signal generator

- Frequency counter

- Variable dc power supply

- Oscilloscope

- Stopwatch

- Variac

5.3.2 TEST/ ADJUSTMENT PREREQUISITES: The following pre-requisites must be

completed prior to performing any of the following procedures:

(a) Verify the ac power voltage is within five

percent of the voltage used to select the primary winding taps of power transformers A7T1 and A8T1.

(b) If the RF drive source is generated by a fixed

frequency crystal oscillator PWBs A4A3 and A5A3, verify the PWBs have been set up as detailed in paragraph 3.9.2.1.

frequency synthesizer PWBs (A4A3 and A5A3), verify their switch settings have been set to provide the desired frequency as detailed in paragraph 3.9.2.2.

(d) Verify the pre-installation for keyer PWBs

A4A1 and A5A1, has been completed as detailed in paragraph 3.9.3.

(e) Verify the appropriate primary winding taps of

power transformers A7T1 and A8T1 have been selected and connected as detailed in paragraph

3.9.4.

(f) Verify harmonic filter A9's inductor taps and in-

circuit capacitors have been selected and connected, for the assigned carrier frequency, as detailed in paragraph 3.9.5.

(g) Connect the transmitter's RF output to a

precision, 50-ohm, resistive dummy load that has provision to accurately display the RF power being applied to it and is rated at a minimum of 1000 watts.

(h) Extend exciter modules A4 and A5, from the

transmitter cabinet, to a position that allows access to

O/P POWER potentiometer A4A2R48

and A5A2R48.

(i) Set

O/P POWER potentiometers A4A2R48 and

A5A2R48 fully counter clockwise.

NOTE

RF CURRENT ALARM lamp should be on when the

transmitter is turned on and the RF output is cutback to zero watts (

O/P POWER potentiometer A4A2R48/

A5A2R48 set fully counter clockwise).

(j) Set

PWR TRIM - LOCAL potentiometers A4R5

and A5R5 fully clockwise.

(k) Set switches as tabulated for Initial Settings in

table 4-1.

5.3.3 TRANSMITTER TURN-ON: Apply ac power to the subject transmitter and verify the indicator indications are normal as follows:

NOTE

The transmitter has duplicated exciter/RF power amplifier stages ('A and 'B'). When any of the following procedures are for the active stage ('A' or 'B') only, the reference designation for side 'A' will be identified and the reference designation for side 'B' will be in parenthesis.

The following modules have been duplicated:

REF REF DES DES DESCRIPTION 'A' 'B'

A2 A3 Modulator/Power Amplifier Module A4 A5 Exciter Module A7 A8 Power Supply Module

Page 5-2

15 January 2005

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

(a) Verify the requirements of paragraph 5.3.2 have

been completed and are being met.

(b) Verify AC power source voltage is within five

percent of voltage used to select the primary winding taps of power transformers A7T1 and A8T1 (see paragraph 3.9.4).

entrance and is being applied to transmitter.

(d) Set

POWER-AC LINE switch A6S1 to ON.

(e) All lamps shall be off.

(f) Set power supply module A's

switch (A7S1) to

ON.

POWER-AC LINE

(g)

DC SUPPLY lamp A7DS2 and B- lamp

A2A9DS1 shall turn on.

(h) Set power supply module B's

switch (A8S1) to

ON.

POWER-AC LINE

(i)

DC SUPPLY lamp A8DS2 and B- lamp

A3A9DS1 shall turn on.

(j) All other lamps shall be off.

5.3.4 DC VOLTAGE CHECKS: Check the Bvoltage (no load) and logic/control dc voltages as follows:

5.3.4.1 B- Voltage (No Load) Check: Check the no load B- voltage level as follows:

(a) Verify switches are set as tabulated for Test

Settings in table 4-1.

(b) Verify

O/P POWER potentiometers A4A2R48

(A5A2R48) are set fully counter clockwise.

A7A1TP1 (A8A1TP1) and ground.

(d) Indication on multimeter should be precisely -

51.0 V dc.

(e) If necessary, adjust B- Level potentiometer

A7A1R12 (A8A1R12) for a multimeter indication of precisely -51.0 V dc.

(f) Set

(g)

TEST-Volts/Current switch to B-V - SIDE A

(

B).

TEST-Volts/Current meter indication shall be

between -50.0 and -52.0 V dc.

NOTE

Adjustment of Meter Cal potentiometer affects TEST-

Volts/Current meter's +24, +15 and -15 indications.

(h) If necessary, adjust

A1A1R2 for a

Meter Cal potentiometer

TEST-Volts/Current meter

indication of -52.0 V dc.

5.3.4.2 Logic/Control Dc Voltage Checks: Check the logic/control dc voltages as follows:

(a) Verify requirements of paragraphs 5.3.2 and

5.3.3 are completed and being met.

(b) Set

(c)

RF switch to ON.

RF CURRENT-ALARM lamp, RF ON lamp, MONITOR-BYPASS lamp and CONVERTER +24V

lamp A7DS1 (A8DS1) shall turn

ON.

(d)

AUDIO LIMITER lamp A4DS1 (A5DS1) and RF DRIVE-ALARM lamp A4DS2 (A5DS2) will turn

on initially. After a delay of approximately five seconds, they shall both turn off.

(e) Blower fan A2B1 (A3B1) shall turn on and

circulate cooling air.

(f) Set

TEST-Volts/Current switch to +24V - SIDE A

(

B).

(g) Connect a multimeter between meter M2 (+)

and ground.

(h) Multimeter's indication shall be between 23.8

and 24.2 V dc.

(i) If necessary, adjust

24 VDC Level potentiometer

A2A1R10 on power supply A7 (A8), for a multimeter indication of 24.0 ± 0.2 V dc.

(j)

TEST-Volts/Current meter's indication shall be

within 10% of the reading in step (h).

(k) Record difference between reading obtained in

step (h) and reading obtained in step (j) as

Volts/Current meter's correction factor for +24

in Established References section of

VOLTS

TEST-

table 5-2.

Page 5-3

15 January 2005

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

(l) Set

TEST-Volts/Current switch to +15V - SIDE A

(

B).

(m) Verify multimeter is connected between meter

M2 (+) and ground.

(n) Multimeter's indication shall be between 14.7

and 15.3 V dc.

(o)

TEST-Volts/Current meter's indication shall be

within 10% of the reading in step (n).

(p) Record difference between reading obtained in

step (n) and reading obtained in step (o) as

TEST-Volts/Current meter's correction factor for

15 VOLTS in Established References section of

table 5-2.

(q) Set

TEST-Volts/Current switch to -15V - SIDE A

(

B).

(r) Connect multimeter between meter M2 (-) and

ground.

(s) Multimeter's indication shall be between -14.25

and -15.75 V dc.

(t)

TEST-Volts/Current meter's indication shall be

within 10% of the reading in step (s).

(u) Record difference between reading obtained in

step (t) and reading obtained in step (s) as

Volts/Current VOLTS

meter's correction factor for -15

in Established References section of

TEST-

table 5-2.

(v) Connect multimeter between test point

A10TP13 and ground.

(w) Multimeter's indication shall be between 14.5

and 15.5 V dc.

(x) Connect a multimeter between test point

A7A1TP2 (A8A1TP2) and ground.

(y) Multimeter's indication shall be between 14.5

and 15.5 V dc.

(z) Connect a multimeter between test point

A10TP7 and ground.

(aa) Multimeter's indication shall be between -14.25

and -15.75 V dc.

Page 5-4

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5.3.5 CARRIER FREQUENCY CHECK: Check the carrier (RF drive) frequency as follows:

5.3.5.1 RF Synthesizer Check: If the RF drive is provided by RF synthesizer PWBs (A4A3 and A5A3), check the RF drive frequency and level, as follows:

(a) Verify switches are set as tabulated for Test

Setting in table 4-1.

(b) Disconnect connector A4P2 (A5P2) from its

mating connector A4A4J1 (A5A4J1).

RF switch to ON. RF DRIVE ALARM lamp

A4DS2 (A5DS2) shall turn on.

(d) Connect a frequency counter between test point

A4A3TP7 (A5A3TP7) and ground.

(e) Frequency counter indication should be within

0.0005% of assigned RF carrier frequency. If necessary, set switches S1 through S5 on the RF synthesizer PWB.

(f) Connect an oscilloscope between test point

A4A3TP7 (A5A3TP7) and ground.

(g) Oscilloscope waveform indication shall be

similar to the waveform depicted in figure 6-4, with a peak-to-peak voltage between 12.1 and

14.9 volts.

(h) Set

RF switch to OFF.

(i) Connect connector A4P2 (A5P2) to its mating

connector A4A4J1 (A5A4J1).

5.3.5.2 RF Oscillator Check: If the RF drive is provided by fixed frequency, RF oscillator PWBs (A4 and A5), check the RF drive frequency and level, as follows:

(a) Verify switches are set as tabulated for Test

Setting in table 4-1.

(b) Verify the appropriate oscillator crystal, for the

assigned carrier frequency, is installed in crystal holder A4A3XY1 (A5A3XY1).

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

oscillator A4A3 (A5A3) (PWB pad 'E' connected to PWB pad ÷4, 8 or 16; PWB pad 'A' connected to PWB pad 'B') for the assigned carrier frequency.

(d) Disconnect connector A4P2 (A5P2) from its

mating connector A4A4J1 (A5A4J1).

(e) Set

RF switch to ON. RF DRIVE ALARM lamp

A4DS2 (A5DS2) shall turn

ON.

(f) Connect a frequency counter between test point

A4A3TP3 (A5A3TP3) and ground.

(g) Frequency counter indication shall be the

assigned carrier frequency ± 0.004%.

(h) If necessary, adjust

Osc Freq trimmer capacitor

A4A3C5 (A5A3C5) until the frequency counter's indication is the assigned carrier frequency ± 0.004%.

(i) Connect an oscilloscope between test point

A4A3TP3 (A5A3TP3) and ground.

(j) Oscilloscope waveform indication shall be

similar to the waveform depicted in figure 6-2, with a peak-to-peak voltage between 11.7 and

14.3 volts.

(k) Set

RF switch to OFF.

(l) Connect connector A4P2 (A5P2) to its mating

connector A4A4J1 (A5A4J1)

5.3.6 RF DRIVE OUTPUT LEVEL CHECK: Check the RF drive output level from RF drive amplifier A4A4 (A5A4) as follows:

(a) Set or verify switches are set as tabulated for

Test Setting in table 4-1.

(b) Set

RF switch to ON.

conductor of A4A4J2 (A5A4J2) and ground.

(d) Oscilloscope waveform indication shall be

similar to the waveform depicted in figure 6-5, with a peak-to-peak voltage between 48.0 and

52.0 volts.

(e) Connect a multimeter between connector

A4A4J3 (A5A4J3) and ground.

(f) Multimeter indication shall be between 12.0 and

14.0 V dc.

(g) Disconnect multimeter and oscilloscope.

5.3.7 PULSE WIDTH MODULATION DRIVE CHECK: Check the frequency and ramp

waveform of the variable pulse width modulation (PWM) mod drive circuit, as follows:

(a) Set or verify switches are set as tabulated for

Test Setting in table 4-1.

(b) Verify

O/P POWER potentiometer A4A2R48

(A5A2R48) is set fully counter clockwise.

PWR TRIM - LOCAL potentiometer A4R5

(A5R5) is set fully clockwise.

(d) Set

RF switch to ON.

(e) Connect a frequency counter between test point

A4A2TP5 (A5A2TP5) and ground.

(f) Frequency counter's indication shall be between

69.86 kHz and 70.14 kHz.

(g) If necessary, adjust

PWM Freq trimmer capacitor

A4A2C22 (A5A2C22) until frequency counter's indication is between 69.86 kHz and 70.14 kHz.

(h) Connect an oscilloscope between test point

A4A2TP6 (A5A2TP6) and ground.

(i) Oscilloscope waveform indication shall be a dc

trace (no pulses).

(j) If necessary, adjust

RAMP ADJUST

potentiometer A4A2R58 (A5A2R58) until there are pulses on the oscilloscope trace and then adjust

RAMP ADJUST potentiometer A4A2R58

(A5A2R58) until the pulses just disappear.

(k) Connect oscilloscope between test point

A4A2TP5 (A5A2TP5) and ground.

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500 WATT RADIOBEACON TRANSMITTER

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(l) Oscilloscope waveform indication shall be

similar to the waveform depicted in figure 6-9, with the negative going peaks at or slightly below the zero volt reference line.

5.3.8 RF CARRIER CHECK: Check that the power amplifier and tuned RF circuits are functioning within the required limits and verify the RF output can be adjusted to the rated carrier level (maximum of 500 watts), as follows:

(a) Verify requirements of paragraph 5.3.2 through

5.3.7 are completed and are being met.

(b) Verify

O/P POWER potentiometer A4A2R48

(A5A2R48) is fully counter clockwise.

PWR TRIM - LOCAL potentiometer A4R5

(A5R5) is fully clockwise.

(d) Set switches as tabulated for Test Setting in

table 4-1.

(e) Set

RF switch to ON.

Discontinue adjusting A4A2R48 (A5A2R48) if reading on

O/P POWER potentiometer

TEST-Power/Mod

meter exceeds 50 watts.

(f) Monitor reflected power indication on

Power/Mod meter and adjust O/P POWER

TEST-

potentiometer A4A2R48 (A5A2R48) for a forward power indication of precisely 500 watts on the dummy load's power indicator.

(g) Forward power level shall linearly increase,

from near zero watts to 500 watts, as

POWER potentiometer A4A2R48 (A5A2R48) is

O/P

adjusted in step (f).

(h)

RF CURRENT-ALARM lamp shall turn off and TEST-Power/Mod meter's reflected power

indication shall be near zero watts.

(i) Set

TEST-Power/Mod switch to FWD PWR.

(j)

TEST-Power/Mod meter's forward power

indication should be 500 watts.

(k) If necessary, adjust

potentiometer A10R79 until

FWD PWR CAL

TEST-Power/Mod

meter's forward power indication is precisely 500 watts.

(l) Set

TEST-Volts/Current switch to DC CURRENT -

SIDE A

(B).

(m)

TEST-Volts/Current meter's indication shall be

between 10.7 and 14.7 amperes.

(n) Set

TEST-Volts/Current switch to B-V - SIDE A

(B).

(o)

TEST-Volts/Current meter's indication shall be

between -49.0 and -51.0 V dc.

(p) Connect an oscilloscope to

RF MONITOR

connector.

(q) Oscilloscope waveform indication shall be

similar to the waveform depicted in figure 6-15, with a peak-to-peak voltage between 18.0 and

22.0 volts.

(r) Adjust

O/P POWER potentiometer A4A2R48

(A5A2R48) for the intended carrier level as indicated on dummy load's forward power indicator.

(s) Repeat steps (1) through (q) with the RF output

set to the intended carrier level.

5.3.9 MODULATION DEPTH (MCW) CHECK: Check the modulation depth with the

transmitter operating in the MCW mode as follows:

NOTE

The intended modulation depth was determined at initial installation. It is the modulation depth a specific antenna system will accommodate before excessive reflected sideband power and/or distortion is produced. It should be as close to 95% as possible. If an intended modulation depth has not been established, set it to 95%.

(a) Set switches as tabulated for Test Setting in

table 4-1.

(b) Verify

position (

RF MON switch A9A2S1 is set to the

VOLT or CUR) determined during

initial installation (see paragraph 3.13).

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500 WATT RADIOBEACON TRANSMITTER

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NOTE

When reading modulation percentage on

Power/Mod meter, always set TEST-Power/Mod switch

MOD-SET and adjust SET 100% MOD potentiometer

TEST-

for a 100% indication before taking a modulation depth reading.

MOD switch A4S2 (A5S2) to ON.

(d) Connect an oscilloscope to

RF MONITOR

connector.

(e) Set

RF switch to ON.

(f) Verify the transmitter's RF output is the

intended carrier level, as indicated by the dummy load's forward power indication.

(g) If necessary, adjust

O/P POWER potentiometer

A4A2R48 (A5A2R48) to set transmitter's RF output to the intended carrier level.

(h) Set

TEST-Power/Mod switch to MOD-SET.

(i) Adjust

modulation depth indication on

Power/Mod meter.

SET 100% MOD potentiometer for a 100%

TEST-

(j) Set

TEST-Power/Mod switch to MOD-READ.

(k) Adjust

(A5A2R19) until

TONE LEVEL potentiometer A4A2R19

TEST-Power/Mod meter's

modulation percentage indication is 100%.

(l) Oscilloscope waveform shall be similar to the

waveform depicted in figure 6-14. Modulation depth shall be 100% and waveform shall be free from clipping and/or distortion.

(m) If necessary, adjust

A4A2R19 (A5A2R19) for a

TONE LEVEL potentiometer

TEST Power/Mod

meter's indication of 95% or the intended modulation depth.

(n) Oscilloscope waveform shall be similar to the

one depicted in figure 6-14. Modulation envelope shall be 95% or the intended modulation depth and waveform shall be free from clipping and distortion.

5.3.10 B- VOLTAGE (MCW) CHECK: Check the B- voltage with the transmitter's RF output set to the intended carrier level and the intended modulation depth, as follows:

(a) Set or verify switches are set as tabulated for

Test Setting in table 4-1.

(b) Set

RF switch to ON.

intended carrier level, as indicated by the dummy load's forward power indication.

(d) If necessary, adjust

O/P POWER potentiometer

A4A2R48 (A5A2R48) to set transmitter's RF output to the intended carrier level.

(e) Set

MOD switch A4S2 (A5S2) to ON.

(f)

Test-Power/Mod meter's indication should be

95% or the intended modulation depth.

(g) If necessary, adjust modulation depth as detailed

in paragraph 5.3.9.

(h) Set

TEST-Volts/Current switch to B- SIDE A (B).

(i) Connect a multimeter between test point

A7A1TP1 (A8A1TP1) and ground.

(j) Multimeter's indication shall be precisely -50.0

V dc.

(k) If necessary, adjust

B- Adj potentiometer

A7A1R12 (A8A1R12) until multimeter's indication is precisely -50.0 V dc.

(l)

Test-Volts/Current meter's indication shall be

between -49.0 and -51.0 V dc.

(m) Record difference between reading obtained in

step (l) and reading obtained in step (j) as

Volts/Current

meter's correction factor for B-

TEST-

volts (MCW) in Established References section of table 5-2.

5.3.11 AUDIO LIMITER BALANCE CHECK: Check the audio limiter circuits as follows:

(a) Set switches as tabulated for Test Setting in

table 4-1.

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500 WATT RADIOBEACON TRANSMITTER

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(b) Connect a shorting jumper between TB4-19

(press-to-talk) and ground.

TB4-22 and TB4-23 with shield if applicable to TB4-24 (see figure 3-3).

(d) Set audio signal generator to 1000 Hz and its

output level to 0 dBm (0.77 Volt RMS).

(e) Set

(f) Set

RF switch and MOD switch A4S2 (A5S2) to

ON.

TONE MOD% potentiometer A4A2R20

(A5A2R20) fully counter clockwise.

(g) Verify the transmitter's RF output is the

intended carrier level, as indicated by the dummy load's forward power indication.

(h)

AUDIO LIMITER lamp A4DS1 (A5DS1) shall be

on.

(i) Connect an oscilloscope to

RF MONITOR

connector.

(j) Simultaneously monitor oscilloscope waveform

and increase output level of audio signal generator to 1.0 dBm.

(k) Oscilloscope waveform indication in step (j)

shall not vary more than 5% while increasing output level of audio signal generator.

(l) If the requirements of step (k) are not met, set

the output of the audio signal generator to 1000 Hz at 0 dBm (0.77 V RMS) and then slowly adjust (A5A2R2) clockwise until

VOICE LEVEL potentiometer A4A2R2

AUDIO LIMITER lamp

A4DS1 (A5DS1) just turns on.

NOTE

Adjust

VOICE LEVEL potentiometer A4A2R2

(A5A2R2) very slowly. A five second time delay is built into the audio voice limiter circuit.

(m) Repeat steps (j) and (k).

5.3.12 MODULATION DEPTH (A3E MODE) CHECK: Check the modulation depth when voice

and tone (A3E mode) are simultaneously transmitted as follows:

NOTE

The intended modulation depth is determined at initial installation. It is the modulation depth a specific antenna system will accommodate before excessive reflected sideband power and/or distortion is produced. The voice/tone must be maintained at a 60/35 percent ratio, relative to the intended modulation depth.

(a) Set switches as tabulated for Test Setting in

table 4-1.

(b) Verify a shorting jumper (press-to-talk) is

connected between TB4-19 and ground.

input) is connected between TB4-22 and TB423 with shield if applicable to TB4-24 (see figure 3-3).

(d) Set audio signal generator to 1000 Hz and its

output level to 0 dBm (0.77 V RMS).

(e) Connect an oscilloscope to

RF MONITOR

connector.

(f) Set

RF switch to ON.

(g) Verify the transmitter's RF output is the

intended carrier level, as indicated by the dummy load's forward power indication.

(h) If necessary, adjust

O/P POWER potentiometer

A4A2R48 (A5A2R48) to set transmitter's RF output to the intended carrier level.

(i) Set

MOD switch A4S2 (A5S2) to ON.

(j) Oscilloscope waveform's modulation envelope

shall be the composite of the external voice audio and the tone audio (A3E). Maximum modulation peaks shall not exceed the intended modulation depth.

(k) If the requirements of step (j) are not met, set

TONE MOD % potentiometer A4A2R20

(A5A2R20) fully counterclockwise.

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500 WATT RADIOBEACON TRANSMITTER

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(l) Oscilloscope waveform's modulation envelope

(external voice audio) shall be 60% of intended modulation depth.

(m) If necessary, adjust

VOICE MOD % potentiometer

A4A2R21 (A5A2R21) until oscilloscope waveform's modulation envelope is 60% of intended modulation depth.

(n) Switch off signal generator's output.

(o) Oscilloscope waveform's modulation envelope

(tone audio) should be 35% of intended modulation depth.

(p) If necessary, adjust

TONE MOD% potentiometer

A4A2R20 (A5A2R20) until oscilloscope waveform's modulation envelope is 35% of intended modulation depth.

(q) Switch on audio signal generator and set its

output to 1000 Hz at 0 dBm (0.77 V RMS).

(r) Oscilloscope waveform's modulation envelope

shall be the composite of the external voice audio and the tone audio (A3E). Maximum modulation peaks shall not exceed the intended modulation depth.

(s) Disconnect audio signal generator.

(t) Remove shorting jumper from TB4-19.

5.3.13 IDENTIFICATION CODE CHECK: Check station identification code as follows:

(a) Set switches as tabulated for Test Setting in

table 4-1.

(b) Set

RF switch to ON.

MOD switch A4S2 (A5S2) to ON.

(d) Verify the RF carrier and modulation depth are

set to their intended levels.

(e) Set

KEYING switch A4S1 (A5S1) to ON.

(f) Set

SPEAKER switch to ON.

15 January 2005

Page 5-9

(g) Adjust

SPEAKER VOLUME potentiometer for a

clear audible keyed beacon identification tone.

(h) The deciphered coded portion of the

identification message shall be the station identification characters as assigned in paragraph 3.9.3.1. Refer to table 5-3 for a list of

Morse code characters.

(i) Using a stopwatch, measure and record the time

for one frame length (from the start of the code of one frame to the start of the code of the next frame).

(j) The time recorded in step (i) shall be between 5

and 16 seconds (typically 8 seconds; see paragraph 3.9.3.1).

5.3.14 STANDBY '1' AND STANDBY '2' CODE CHECKS: Check for generation of the

standby 1 and standby 2 code variations as follows:

(a) Verify requirements of paragraphs 5.3.2 through

5.3.12 have been completed.

(b) Set switches as tabulated for Test Settings in

table 4-1.

RF switch to ON.

(d) Set

MOD switch A4S2 (A5S2) to ON.

(e) Verify the RF carrier output and modulation

depth are set to their intended levels.

(f) Set

KEYING switch A4S1 (A5S1) to ON.

(g) Set

SPEAKER switch to ON and verify an

audible keyed beacon tone can be heard from the speaker.

(h) Connect a shorting jumper (standby 1) between

TB3-7 (TB3-11) and ground.

(i) Standby 1 code variation, as assigned in

paragraph 3.9.3.1 and recorded in table 5-2, shall be included in the identification portion of the ident code.

(j) Disconnect jumper from TB3-7 (TB3-11).

(k) Connect a shorting jumper (standby 2) between

TB3-8 (TB3-12) and ground.

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

(l) Standby 2 code variation, which is a 0.125

second blip that occurs 0.875 seconds before the first ident character, shall be detected in the ident code.

(m) Disconnect shorting jumper from TB3-8 (TB3-

12).

5.3.15 FAULT THRESHOLDS/ CHANGEOVER CHECK: Check that the carrier level and

modulation depth fault thresholds are set to the desired levels that will result in a main to standby transmitter changeover occurring when RF output falls below a predetermined minimum carrier level; when the modulation envelope falls below a predetermined percentage or keying is not present, for a predetermined period of time; as follows:

5.3.15.1 Preliminary Changeover Procedures: Verify the previous functional test/adjustment prerequisites have been completed and then check that the associated potentiometers and switches have been set to the settings required to start the changeover procedures as follows:

(a) Verify carrier level checks of paragraph 5.3.8

have been completed and are being met.

(b) Verify modulation depth requirements (tone

only) of paragraph 5.3.9 have been completed and are being met.

RF MONITOR

connector.

(d) Set switches as tabulated for Test Setting in

table 4-1.

(e) Set

TEST-Power/Mod switch to FWD PWR.

(f) Set

RF switch to ON.

(g) Verify the transmitter's RF output is the

intended carrier level, as indicated by

Power/Mod

meter's forward power indication.

TEST-

(h) If necessary, adjust

O/P POWER potentiometer

A4A2R48 (A5A2R48) to set transmitter's RF output to the intended carrier level.

(i) Set

MOD switch A4S2 (A5S2) to ON.

(j) Oscilloscope waveform's modulation envelope

shall be the intended modulation depth.

(k) If necessary, adjust

TONE LEVEL potentiometer

A4A2R19 (A5A2R19) until the modulation envelope on the oscilloscope waveform is the intended modulation depth.

(l) Set

KEYING switch A4S1 (A5S1) to ON.

(m)

SET THRSH lamp A10DS1 shall be flashing on

and off, provided the keying frame contains identification code.

NOTE

Refer to figure MD-34 to locate monitor PWB A10 and

SET THRSH lamp A10DS1.

5.3.15.2 Carrier Level Fault Threshold Check: Verify the carrier level fault threshold is set to initiate a changeover from the selected side (main transmitter) to the other side (standby transmitter) when the carrier level has decreased by 3.0 dB from the intended carrier level or to a user determined minimum level, as follows:

NOTE

International Civil Aviation Organization (ICAO) standards dictate the transmitter to be turned off or a warning alarm be generated when the RF output has decreased by 3.0 dB or more from the intended carrier level. The following procedures use -3.0 dB as the carrier level fault threshold. If the user decides to select a different threshold level, the user selected threshold level shall be inserted where -3.0 dB is referenced. The desired carrier fault threshold level shall be recorded in 'Established References section of table 5-2.

(a) Verify requirements of paragraph 5.3.15.1 have

been completed and are being met.

(b) Verify

PWR

TEST-Power/Mod switch is set to FWD

indication on

THRSH

carrier level by adjusting

TEST-Power/Mod meter and of SET

lamp A10DS1, while decreasing RF

O/P POWER

potentiometer A4A2R48 (A5A2R48) counter clock-wise until

SET THRSH lamp just turns full

on and remains on or forward power indication has decreased by more than -3.0 dB.

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500 WATT RADIOBEACON TRANSMITTER

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(d)

TEST-Power/Mod meter's forward power

indication should be -3.0 dB from the intended carrier level.

(e) If requirement of step (d) is met, go to step (k);

if not, complete steps (f) through (j).

(f) Adjust

O/P POWER potentiometer A4A2R48

(A5A2R48) for a forward power indication on

TEST-Power/Mod meter that is 3.0 dB less than

the intended carrier level.

(g) If

SET THRSH lamp A10DS1 is full on (not

flashing), adjust A10R18 until

CARR THRSH potentiometer

SET THRSH lamp A10DS1 is

flashing.

(h) Adjust

until

CARR THRSH potentiometer A10R18

SET THRSH lamp A10DS1 just turns full

on and remains on.

(i) Adjust

O/P POWER potentiometer A4A2R48

(A5A2R48) for the intended carrier level, as indicated by

TEST-Power/Mod meter.

(j) Repeat steps (b) through (d).

(k) Adjust

O/P POWER potentiometer A4A2R48

(A5A2R48) for the intended carrier level, as indicated by

TEST-Power/Mod meter.

(l)

SET THRSH lamp A10DS1 shall be flashing on

and off.

5.3.15.3 Modulation Depth Fault Threshold Check: Check that the modulation depth fault

threshold is set to initiate a changeover from main to standby transmitter when the modulation depth has decreased by 4.0 dB or to a user determined decrease, as follows:

NOTE

The modulation depth fault threshold (normally -4.0 dB) must be not less than -1.0 dB greater than the carrier level fault threshold.

(a) Verify the instructions detailed in paragraphs

5.3.15.1 and 5.3.15.2 have been completed and their requirements are being met.

(b) Determine the minimum modulation depth

(normally -4.0 dB when the carrier level fault threshold is -3.0 dB) that is acceptable before transmitter changeover occurs. Record this level as the Modulation Depth Fault Threshold in Established References section of table 5-2.

NOTE

If difference between intended modulation depth and modulation depth fault threshold is specified in dB, refer to table 5-1 and determine power multiplication factor for specified dB reduction. Multiply intended modulation depth by power multiplication factor to determine modulation depth fault threshold.

table 4-1.

(d) Set

MOD switch A4S2 (A5S2) to ON.

(e) Verify an oscilloscope is connected to

MONITOR connector.

(f) Set

RF switch to ON.

(g) Verify the RF output is the intended carrier

level, as indicated by

TEST-Power/Mod meter.

(h) Verify oscilloscope waveform's modulation

envelope is the intended modulation depth.

(i) Set

KEYING switch A4S1 (A5S1) to ON.

(j)

SET THRSH lamp A10DS1 shall be flashing on

and off.

(k) Simultaneously monitor oscilloscope

waveform's modulation envelope (when modulation is present) and

SET THRSH lamp,

while decreasing the modulation depth. Adjust

TONE LEVEL potentiometer A4A2R19

(A5A2R19) until

SET THRSH lamp just turns

full on or the mod depth is less than the fault threshold determined in step (b).

(l) Set

KEYING switch A4S1 (A5S1) to OFF.

(m) Oscilloscope waveform's modulation envelope

should be the modulation depth for the modulation depth fault threshold determined in step (b).

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(n) If requirement of step (m) is met, go to step (v);

if not, complete steps (o) through (u).

(o) Adjust

TONE LEVEL potentiometer A4A2R19

(A5A2R19) for a modulation envelope, on oscilloscope waveform, that is precisely the modulation depth for the modulation depth fault threshold determined in step (b).

(p) Set

KEYING switch A4S1 (A5S1) to ON.

(q) If

SET THRSH lamp A10DS1 is full on (not

flashing), adjust A10R7 until

MOD THRSH potentiometer

SET THRSH lamp A10DS1 is

flashing.

(r) Adjust

SET THRSH lamp A10DS1 just turns full on and

MOD THRSH potentiometer A10R7 until

remains on.

(s) Set

KEYING switch A4S1 (A5S1) to OFF.

(t) Adjust

TONE LEVEL potentiometer A4A2R19

(A5A2R19) for a modulation envelope, on oscilloscope waveform, that is the intended modulation depth.

NOTE

The changeover delay period, once set, is applicable to both sides of the transmitter. If either side 'A' or 'B' of the transmitter shuts down, the pre-selected delay will occur before applicable,

SHUTDOWN ALARM lamp turns on.

STANDBY ALARM lamp or, if

(a) Verify requirements of paragraphs 5.3.15.1 and

5.3.15.3 are completed and being met.

(b) Set switches as tabulated for Test Setting in

table 4-1.

recorded as the changeover time delay in Established References section.

NOTE

If a changeover time delay has not been established or is to be changed, determine the delay to be used and record this time as the changeover time delay in

Established References section of table 5-2.

(d) Set

MOD switch A4S2 (A5S2) to ON.

(e) Set

RF switch to ON.

(u) Repeat steps (i) through (m).

(v) Adjust

TONE LEVEL potentiometer A4A2R19

(A5A2R19) for a modulation envelope, on oscilloscope waveform, that is the intended modulation depth.

(w) Set

KEYING switch A4S1 (A5S1) to ON.

(x)

SET THRSH lamp A10DS1 shall be flashing on

and off.

5.3.15.4 Changeover/Shutdown Check: Check auto changeover from side A to side B and/or the shutdown of the transmitter when; the RF output falls below a predetermined minimum carrier level; modulation envelope falls below a predetermined percentage or when keying is not present; for a predetermined period of time, as follows:

(f) Verify transmitter is operating at the intended

carrier level and the intended modulation depth.

(g) Set

KEYING switch A4S1 (A5S1) to ON.

(h) Set

MONITOR switch to NORMAL.

(i)

MONITOR-BYPASS lamp A1A1DS8 shall turn

off and selected side A or B shall remain on.

(j) Simultaneously start stopwatch, monitor

STANDBY ALARM lamp and set KEYING switch

A4S1 (A5S1) to

OFF.

(k) After the delay determined in step (c), the

selected side (main) transmitter will turn off and

STANDBY-ALARM lamp shall turn on.

NOTE

RF CURRENT-ALARM lamp, RF DRIVE-ALARM lamp

A5DS2 (A4DS2) and

AUDIO LIMITER lamp A5DS1

(A4DS1) shall also turn on. After a nominal five second delay, these lamps shall turn off and the standby transmitter shall turn on; provided it is switched on and is serviceable.

Page 5-12

15 January 2005

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

Table 5-1 dB to Power/Voltage Conversion

VOLTAGE -dB POWER VOLTAGE -dB POWER VOLTAGE -dB POWER

1.0000 0.0 1.0000 0.6310 4.0 0.3981 0.3981 8.0 0.1585

0.9886 0.1 0.9772 0.6237 4.1 0.3890 0.3936 8.1 0.1549

0.9772 0.2 0.9550 0.6166 4.2 0.3802 0.3890 8.2 0.1514

0.9661 0.3 0.9333 0.6095 4.3 0.3715 0.3846 8.3 0.1479

0.9550 0.4 0.9120 0.6026 4.4 0.3631 0.3802 8.4 0.1445

0.9441 0.5 0.8913 0.5957 4.5 0.3548 0.3758 8.5 0.1413

0.9333 0.6 0.8710 0.5888 4.6 0.3467 0.3715 8.6 0.1380

0.9226 0.7 0.8511 0.5821 4.7 0.3388 0.3673 8.7 0.1349

0.9120 0.8 0.8318 0.5754 4.8 0.3311 0.3631 8.8 0.1318

0.9016 0.9 0.8128 0.5689 4.9 0.3236 0.3589 8.9 0.1288

0.8913 1.0 0.7943 0.5623 5.0 0.3162 0.3548 9.0 0.1259

0.8810 1.1 0.7762 0.5559 5.1 0.3090 0.3508 9.1 0.1230

0.8710 1.2 0.7586 0.5495 5.2 0.3020 0.3467 9.2 0.1202

0.8610 1.3 0.7413 0.5433 5.3 0.2951 0.3428 9.3 0.1175

0.8511 1.4 0.7244 0.5370 5.4 0.2884 0.3388 9.4 0.1148

0.8414 1.5 0.7079 0.5309 5.5 0.2818 0.3350 9.5 0.1122

0.8318 1.6 0.6918 0.5248 5.6 0.2754 0.3311 9.6 0.1096

0.8222 1.7 0.6761 0.5188 5.7 0.2692 0.3273 9.7 0.1072

0.8128 1.8 0.6607 0.5129 5.8 0.2630 0.3236 9.8 0.1047

0.8035 1.9 0.6457 0.5070 5.9 0.2570 0.3199 9.9 0.1023

0.7943 2.0 0.6310 0.5012 6.0 0.2512 0.3162 10.0 0.1000

0.7852 2.1 0.6166 0.4955 6.1 0.2455 0.3126 10.1 0.09972

0.7762 2.2 0.6026 0.4898 6.2 0.2399 0.3090 10.2 0.09550

0.7674 2.3 0.5888 0.4842 6.3 0.2344 0.3055 10.3 0.09333

0.7586 2.4 0.5754 0.4786 6.4 0.2291 0.3020 10.4 0.09120

0.7499 2.5 0.5623 0.4732 6.5 0.2239 0.2985 10.5 0.08913

0.7413 2.6 0.5495 0.4677 6.6 0.2188 0.2951 10.6 0.08710

0.7328 2.7 0.5370 0.4624 6.7 0.2138 0.2917 10.7 0.08511

0.7244 2.8 0.5248 0.4571 6.8 0.2089 0.2884 10.8 0.08318

0.7161 2.9 0.5129 0.4519 6.9 0.2042 0.2851 10.9 0.08128

0.7079 3.0 0.5012 0.4467 7.0 0.1995 0.2818 11.0 0.07943

0.6998 3.1 0.4898 0.4416 7.1 0.1950 0.2786 11.1 0.07762

0.6918 3.2 0.4786 0.4365 7.2 0.1905 0.2754 11.2 0.07586

0.6839 3.3 0.4677 0.4315 7.3 0.1862 0.2723 11.3 0.07413

0.6761 3.4 0.4571 0.4266 7.4 0.1820 0.2692 11.4 0.07244

0.6683 3.5 0.4467 0.4217 7.5 0.1778 0.2661 11.5 0.07079

0.6607 3.6 0.4365 0.4169 7.6 0.1738 0.2630 11.6 0.06918

0.6531 3.7 0.4266 0.4121 7.7 0.1698 0.2600 11.7 0.06761

0.6457 3.8 0.4169 0.4074 7.8 0.1660 0.2570 11.8 0.06607

0.6383 3.9 0.4074 0.4027 7.9 0.1622 0.2541 11.9 0.06457

Page 5-13

15 January 2005

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

(l) If the changeover delay time in step (k) is

satisfactory, go to step (p); if not, complete steps (m) through (o).

(m) Set

RF switch to OFF and MONITOR switch to

BYPASS.

(n) Adjust

CHANGEOVER DELAY potentiometer

A10R48 in the direction required to produce the desired changeover time delay.

NOTE

CHANGEOVER DELAY potentiometer A10R48 can be

adjusted for a changeover time delay that is between 20 and 80 seconds. Clockwise adjustment increases the time and counter clockwise adjustment decreases the time.

(o) Repeat steps (e) through (n) until the

requirements of step (k) are met without further adjustment of

CHANGEOVER DELAY

potentiometer A10R48.

(p) Set

RF switch to OFF and MONITOR switch to

BYPASS.

(q) Set

KEYING switch A4S1 (A5S1) to ON.

(r) Set

RF switch to ON.

(s)

SET THRSH lamp A10DS1 shall be flashing on

and off.

(t) Monitor

decrease carrier level by adjusting

SET THRSH lamp A10DS1 and

O/P POWER

potentiometer A4A2R48 (A5A2R48) counter clockwise until

SET THRSH lamp A10DS1 just

turns full on.

(u)

TEST-Power/Mod meter's forward power

indication shall be the level recorded for carrier fault threshold level in Established References section of table 5-2.

(v) Simultaneously start stopwatch, monitor

STANDBY ALARM lamp and set MONITOR

switch to NORMAL.

(w)

MONITOR-BYPASS lamp A1A1DS8 shall turn

off and selected side A or B shall remain on.

(x) After the delay determined in step (c), the

selected side (main) transmitter will turn off and

STANDBY-ALARM lamp shall turn on [(see note

after step (k)].

(y) Set

(z) Set

RF switch to OFF and MONITOR switch to

BYPASS.

RF switch to ON.

(aa) Adjust

O/P POWER potentiometer A4A2R48

(A5A2R48) for the intended carrier level, as indicated by

TEST-Power/Mod meter.

(ab) Verify

ON.

KEYING switch A4S1 (A5S1) is set to

(ac)

SET THRSH lamp A10DS1 shall be flashing on

and off.

(ad) Monitor

depth by adjusting

SET THRSH lamp and decrease mod

TONE LEVEL potentiometer

A4A2R19 (A5A2R19) counter clockwise until

SET THRSH lamp just turns full on.

(ae) Set

KEYING switch A4S1 (A5S1) to OFF.

(af) Set

TEST-Power/Mod switch to MOD-SET.

(ag) Adjust

100% modulation depth indication on

Power/Mod meter.

SET 100 % MOD potentiometer for a

TEST-

(ah) Set

TEST-Power/Mod switch to MOD-READ.

NOTE

When reading modulation percentage on

Mod

meter, always set TEST-Power/Mod switch to

MOD-SET and adjust SET 100 % potentiometer for a

TEST-Power/

100% indication before taking a modulation depth reading.

(ai)

TEST-Power/Mod meter's modulation indication

shall be percentage recorded for mod fault threshold level in Established References section of table 5-2.

(aj) Set

KEYING switch A4S1 (A5S1) to ON.

(ak) Simultaneously start stopwatch, monitor

STANDBY ALARM lamp and set MONITOR

switch to

NORMAL.

Page 5-14

15 January 2005

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

(al)

MONITOR-BYPASS lamp A1A1DS8 shall turn

off and selected side A or B shall remain on.

(am) After the delay determined in step (c), the

selected side (main) transmitter will turn off and

STANDBY-ALARM lamp shall turn on (see note

after step (k).

(an) Set

RF switch to OFF and MONITOR switch to

BYPASS.

(ao) Set

KEYING switch A4S1 (A5S1) to OFF.

(ap) Set

RF switch to ON.

(aq) Adjust

TONE LEVEL potentiometer A4A2R19

(A5A2R19) for the intended modulation depth, as indicated by

TEST-Power/Mod meter.

5.3.16 SWR CUTBACK THRESHOLD CHECK: Check that SWR cutback threshold level

represents a reflected power of 55 watts, as follows:

(a) Set switches as tabulated for Test Setting in

table 4-1.

(b) Set

O/P POWER potentiometer A4A2R48

(A5A2R48) fully counter clockwise.

RF switch is set to OFF.

(d) Disconnect connector P13 from A9A2J1 and

P14 from A9A2J2 (refer to figure MD-30 to locate fwd/refld power probe A9A2).

(e) Install connector P14 on connector A9A2J1.

(f) Connect a shorting clip across resistor

A4A2R44 (A5A2R44).

(g) Set

RF switch to ON.

(h) Simultaneously monitor dummy load's power

indicator and adjusting (A5A2R48) clockwise until

SWR-ALARM lamp while slowly

O/P POWER potentiometer A4A2R48

SWR ALARM lamp

just turns on.

Discontinue adjusting

O/P POWER potentiometer

A4A2R48 (A5A2R48) when dummy load's forward power indication exceeds 60 watts.

(i) Dummy load's forward power indication should

be 55 watts.

(j) If requirement of step (i) is not met, adjust

POWER potentiometer A4A2R48 (A5A2R48)

O/P

for precisely 55 watts as indicated by dummy load's forward power indication.

(k) Set

TEST-Power/Mod switch to REFL PWR.

(l)

TEST-Power/Mod meter's indication shall be 55

±5.0 watts.

(m) Adjust

potentiometer A10R95 until

SWR CUTBACK THRESHOLD

SWR-ALARM lamp

just turns on.

(n) Connect a multimeter, which has been set to

measure resistance between TB3-13 and ground.

(o) Multimeter indication (

SWR Alarm) shall be

zero ohms.

(p) Connect a multimeter, which has been set to

measure resistance, between TB3-10 and ground.

(q) Multimeter indication (

SWR Standby) shall be

zero ohms.

(r) Set

O/P POWER potentiometer A4A2R48

(A5A2R48) fully counter clockwise.

(s)

SWR-ALARM lamp shall turn off.

(t) Remove shorting clip from resistor A4A2R44

(A5A2R44).

(u) Slowly adjust

A4A2R48 (A5A2R48) clockwise until

ALARM

lamp just turns on.

O/P POWER potentiometer

SWR-

Page 5-15

15 January 2005

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

(v) Simultaneously monitor

TEST-Power/Mod

meter's reflected power indication and continue to adjust

O/P POWER potentiometer A4A2R48

(A5A2R48) clockwise.

(w) Reflected power indication on

TEST-Power/Mod

meter shall not increase significantly beyond 55 watts as

O/P POWER potentiometer A4A2R48

(A5A2R48) is adjusted clockwise.

(x) Set

O/P POWER potentiometer A4A2R48

(A5A2R48) fully counter clockwise.

(y) Set

RF switch to OFF.

(z) Disconnect connector P14 from A9A2J1 and

install it on A9A2J2.

(aa) Install connector P13 to A9A2J1.

(ab) Set

(ac) Adjust

RF switch to ON.

O/P POWER potentiometer A4A2R48

(A5A2R48) for the intended carrier level as indicated by dummy load's forward power probe indication.

5.3.17 RF CURRENT THRESHOLD CHECK: Verify the modulation peak detector circuit

will cause

RF CURRENT-ALARM lamp to turn on when

the absolute maximum modulation peaks (500 watts carrier level with modulation peaks of 100%) are exceeded, as follows:

NOTE

The modulation peak detector (RF current) circuit has no influence on the radiated RF output. Its sole purpose is to alert a maintainer that the modulation envelope is exceeding 100% when the RF output is set to the intended carrier level.

(a) Set switches as tabulated for Test Setting in

table 4-1.

(b) Set

RF switch to ON.

MOD switch A4S2 (A5S2) to ON.

(d) Verify the RF output is the intended carrier level

and it is being modulated by the intended modulation depth.

(e) Adjust

O/P POWER potentiometer A4A2R48

(A5A2R48) for precisely 500 watts, as indicated by dummy load's forward power indication.

(f) Set

TEST-Power/Mod switch to MOD-SET.

(g) Adjust

modulation depth indication on

Mod meter.

SET 100 % MOD potentiometer for 100%

TEST-Power/

(h) Set TEST-Power/Mod switch to MOD-READ.

(i) Simultaneously monitor

while adjusting

TEST-Power/Mod meter

TONE LEVEL potentiometer

A4A2R19 (A5A2R19) for 100% modulation depth indication.

(j)

RF CURRENT-ALARM lamp shall turn on.

(k) If necessary, adjust

potentiometer A10R23 until

ALARM lamp just turns on.

RF CURRENT CAL

RF CURRENT-

(l) Connect an oscilloscope between test point

A10TP14 and ground.

(m) Oscilloscope waveform indication shall be

similar to the waveform depicted in figure 6-13.

(n) Simultaneously monitor

while adjusting

TEST-Power/Mod meter

TONE LEVEL potentiometer

A4A2R19 (A5A2R19) for an indication that is slightly below 100% modulation.

(o)

RF CURRENT-ALARM lamp shall turn off.

(p) Adjust

O/P POWER potentiometer A4A2R48

(A5A2R48) for the intended carrier level, as indicated by dummy load's forward power indication.

(q) Adjust

TONE LEVEL potentiometer A4A2R19

(A5A2R19) for the intended modulation depth, as indicated by

TEST-Power/Mod meter.

5.3.18 ALARM SYSTEMS CHECK: Verify the following alarm lamps turn on when the transmitter's parameters are not met:

Page 5-16

15 January 2005

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

5.3.18.1 RF Current-Alarm Check: RF

CURRENT-ALARM lamp was checked in paragraph

5.3.17.

5.3.18.2 SWR-Alarm Check:

SWR-ALARM lamp

was checked in paragraph 5.3.16.

5.3.18.3 Shutdown-Alarm Check: Check

SHUTDOWN-ALARM lamp as follows:

(a) Set switches as tabulated for Test Setting in

table 4-1.

(b) Set

RF switch to ON.

MOD switch A4S2 (A5S2) to ON.

(d) Verify the RF output is the intended carrier level

and it is being modulated by the intended modulation depth.

(e) Set

KEYING switch A4S1 (A5S1) to ON.

(f) Set

MONITOR switch to NORMAL.

(g) Verify

MONITOR-BYPASS lamp is turned off.

(h) Set

KEYING switch A4S1 (A5S1) to OFF.

(i) After the changeover time delay recorded in

Established References section of table 5-2 (between 20 and 80 seconds), the selected side (main transmitter) will shut down and

STANDBY-ALARM lamp will turn on.

NOTE

When changeover occurs and the standby transmitter fails to turn on, an additional 20 to 80 second delay will occur plus a nominal five second delay before a shutdown-alarm control signal is generated.

(j) After an additional changeover time delay

period (between 20 and 80 seconds),

SHUTDOWN-ALARM lamp will turn on.

(k) Set

RF switch to OFF.

(l) Set

KEYING switch A4S1 (A5S1) to ON.

(m) Set

MONITOR switch to BYPASS.

(n) Set

RF switch to ON.

(o) MONITOR-BYPASS lamp shall turn on,

STANDBY-ALARM lamp and SHUTDOWN-ALARM

lamp shall turn off.

(p) The selected side (main transmitter) shall turn

on and resume normal operation.

5.3.18.4 Standby-Alarm Check: The standby changeover and indicator circuits are checked in paragraphs 5.3.18.3.

5.3.18.5 Battery-Alarm Check: When the dc option is installed,

BATTERY-ALARM lamp function is

checked in paragraph 5.3.19. When the dc option is not installed,

BATTERY-ALARM lamp function is

checked in paragraph 5.4.3.

5.3.18.6 Mod Drive-Alarm Check: Check mod drive fault monitoring/indicating circuits as follows:

NOTE

Completion of these checks will alter PWM ramp integrator circuit. On completion, the ramp integrator circuit must be readjusted in accordance with paragraph 5.3.7.

(a) Set switches as tabulated for Test Setting in

table 4-1.

(b) Set

POWER TRIM potentiometer A4R5 (A5R5)

and

RAMP ADJUST potentiometer A4A2R58

(A5A2R58) fully clockwise.

O/P POWER potentiometer A4A2R48

(A5A2R48) fully counterclockwise.

(d) Connect a shorting clip across resistor

A4A2R59 (A5A2R59).

(e) Connect an oscilloscope between test point

A4A2TP6 (A5A2TP6) and ground.

(f) Disconnect connector P6 from A4J1 (A5J1).

(g) Set

RF switch to ON.

(h) Adjust

(A5A2R48) clockwise until

O/P POWER potentiometer A4A2R48

MOD DRIVE-ALARM

lamp A4DS3 (A5DS3) turns on.

Page 5-17

15 January 2005

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

(i) Measure and record oscilloscope mod drive

waveform's on/off duty cycle, noting off period is zero volts and on period is ±15 volts.

(j) The on time recorded in step (i) shall be

between 59 and 65%.

(k) Oscilloscope waveform indication shall be

similar to the waveform depicted in figure 6-11.

(l) Set

RF switch to OFF.

(m) Install connector P6 on A4J1 (A5J1).

(n) Remove shorting clip from resistor A4A2R59

(A5A2R59).

(o) Adjust PWM ramp integrator circuit as detailed

in paragraph 5.3.7.

5.3.18.7 RF Drive-Alarm Check: Check

DRIVE-ALARM lamp A4DS2 (A5DS2) function as

follows:

(a) Set or verify switches are set as tabulated for

Test Setting in table 4-1.

(b) Disconnect P6 (P8) from A4J1 (A5J1).

(d) Disconnect A4P4 (A5P4) from A4A4J3

(A5A4J3).

(e) Connect output from a variable (0 to 50 volts)

DC power supply between connector A4P4 (A5P4) and ground, ensuring positive lead is connected to A4P4 (A5P4).

(f) Set output of variable dc power supply to 15.0

V dc.

(g) Set

RF switch to ON.

(h) Reduce output of dc power supply until

DRIVE-ALARM lamp A4DS2 (A5DS2) just turns

on.

(i) Dc power supply's output voltage shall be

between 9.8 and 10.5 V dc.

(j) Set

RF switch to OFF.

(k) Disconnect dc power supply from A4P4

(A5P4).

(l) Install A4P4 (A5P4) on A4A4J3 (A5A4J3).

(m) Install P6 (P8) on A4J1 (A5J1).

(n) Install P19 (P20) on A4A4J2 (A5A4J2).

5.3.19 LOW AC POWER CHECK: The low AC power check is not performed during functional test/adjustment procedures. The low AC power check will be performed in the special adjustment procedures (refer to paragraph 5.4.3).

5.3.20 LOW BATTERY VOLTAGE MONITOR: When applicable, verify transmitter

shuts down when external dc power source voltage decreases to -42.0 V dc, as follows:

NOTE

The low battery threshold level is set to -42 V dc at the factory. When the battery voltage falls below this level, a shutdown-alarm lamp shall turn on and the transmitter shall turn off. Users have the option of setting the low battery voltage threshold at a lower level (see paragraph 5.4.4).

(a) Verify battery panel related links are removed

from between the terminals of TB3-1/TB3-2 and TB3-3/TB3-4 on TB3 (see note on figure SD-1).

(b) Set switches as tabulated for Test Setting in

table 4-1.

POWER-BATTERY switch A6S2 to ON.

(d) Set

RF switch to ON.

(e) Set

MOD switch A4S2 (A5S2) to ON.

(f) Verify transmitter is operating at the intended

carrier level and the intended modulation depth.

(g) Set

POWER-AC LINE switch A6S1 to OFF.

(h)

BATTERY ALARM lamp shall turn on and a

remote battery alarm control signal (ground) will be applied to TB3-14.

Page 5-18

15 January 2005

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

(i) Verify transmitter is operating at the intended

carrier level (500 watts maximum) and the intended modulation depth.

(j) Connect a multimeter between TB2-1(+) and

TB2-2(-).

(k) Indication on multimeter, just prior to

SHUTDOWN-ALARM lamp turning on, shall be a

nominal -42.0 V dc.

(l) When battery voltage decreases below the

nominal -42.0 V dc,

SHUTDOWN ALARM lamp

shall turn on. The transmitter will shut down.

(m) Set

POWER-BATTERY switch A6S2 to OFF.

(n) Remove discharged batteries and reinstall

charged batteries (nominal -48.0 V dc) to the appropriate terminals on TB2).

(o) Set

POWER-BATTERY switch to ON.

(p) Momentarily depress (three to five seconds)

BATTERY RESET switch.

(q) Verify transmitter turns on and is operating at

the intended carrier level and the intended modulation depth.

(r) Remove multimeter.

(s) Set

POWER-AC LINE switch A6S1 to ON.

(t)

BATTERY-ALARM lamp shall turn off and the

remote battery alarm control signal (ground) shall be removed from TB3-14.

(u) Verify transmitter is operating at the intended

carrier level and the intended modulation depth.

5.3.21 TEST/ADJUSTMENT OF SIDE B:

Complete a functional test and if necessary adjust side B of the transmitter as follows:

(a) Set

SELECT MAIN TX switch to B.

(b) Repeat paragraphs 5.3.2 through 5.3.20 using

reference designations and transmitter side identification in parenthesis for modules that are duplicated in sides A and B.

NOTE

SELECT MAIN TX switch must be set to B when

instructed to set switches as tabulated for Test Settings in table 4-1.

SPECIAL ADJUSTMENT PROCEDURES

5.4 Procedures referred to as special adjustment

procedures require test equipment that is not normally available at transmitter sites. The adjustments have been precisely set at the factory prior to shipment and should not require further adjustment. The accuracy of the settings will affect the accuracy of the adjustment settings; therefore, they should not be disturbed unless their accuracy is suspect and then only if specified test equipment is available.

High voltages that may cause serious injury or death are present inside the transmitter cabinet. Use extreme caution when ac power is applied.

NOTE

When an adjustment procedure is for a module or component that is duplicated for sides A and B, the reference designation that is applicable to the side 'B' module is shown in parenthesis (see note after paragraph 5.3.3).

5.4.1 CURRENT SHUNT RESISTOR ADJUSTMENT (see figure SD-1): Adjust current

shunt resistor R1 (R4) as follows:

(a) Set switches, except

POWER-AC LINE switch as

tabulated for Test Settings in table 4-1.

(b) Set

POWER-AC LINE switch A6S1 to OFF.

cabinet.

(d) Set

TEST-Volts/Current switch to DC CURRENT-

SIDE A (B).

(e) Set O/P POWER potentiometer A4A2R48

(A5A2R48) fully counter clockwise.

(f) Using a clip-on dc current meter, clip current

meter over wire going to current shunt resistor R1-5 (R4-5).

Page 5-19

15 January 2005

500 WATT RADIOBEACON TRANSMITTER

ND2000A-02x-xx0

(g) Set

POWER-AC LINE switch A6S1 to ON.

(h) Verify

DC SUPPLY lamp A7DS2 (A8DS2) and

B- lamp A2A9DS1 (A3A9DS1) are on.

(i) Set

RF switch to ON.

(j) Adjust

O/P POWER potentiometer A4A2R48

(A5A2R48) for a 10.0 ampere indication on the clip-on dc current meter.

(k)

TEST-Volts/Current meter's indication shall be

10.0 amperes.

(l) If necessary, adjust

R2 (R3) for a 10.0 indication on

Current meter.

Current Cal potentiometer

TEST-Volts/

(m) Remove clip-on dc current meter.

(n) Set

TEST-Power/Mod switch to FWD PWR.

(o) Set

O/P POWER potentiometer A4A2R48

(A5A2R48) for 500 watts of forward power, as indicated by

TEST-Power/Mod meter.

(p)

TEST-Volts/Current meter's indication shall be

between 10.7 and 14.7 amperes.

(q) Set

MOD switch A4S2 (A5S2) to ON and note

TEST-Power/Mod meter's modulation depth

(percentage) reading.

NOTE

When using

TEST-Power/Mod meter for an indication

of the RF outputs modulation percentage, always set

TEST-Power/Mod switch to MOD-SET and adjust SET

potentiometer for a 100% modulation depth

100 %

indication on

MOD-READ for actual reading.

TEST-Power/Mod meter. Set switch to

(r) If necessary, adjust

TONE LEVEL potentiometer

A4A2R19 (A5A2R19) for a 95% modulation depth indication on

TEST-Power/Mod meter.

(s) Dc current indication on

TEST-Volts/Current

meter shall be 18.0 ± 2.0 amperes.

(t) Adjust

O/P POWER potentiometer A4A2R48

(A5A2R48) for the intended carrier level, as indicated on

TEST-Power/Mod meter.

(u) Adjust

TONE LEVEL potentiometer A4A2R19

(A5A2R19) for the intended modulation depth as indicated on

TEST-Power/Mod meter.

(v) Record

TEST-Volts/Current meter's current

indication, when the RF output is the intended carrier level at the intended modulation depth, for comparison with future test results.

(w) Set

POWER-AC LINE switch A6S1 to OFF.

(x) Install panel on transmitter upon completion of

tests.

5.4.2 TEST METER ADJUSTMENT: Check the accuracy of the forward power and reflected power indications of

TEST-Power/Mod meter and if

necessary, adjust as follows:

NOTE

Test-Power/Mod meter's accuracy was set during

manufacture. Its accuracy will affect the quality of routine adjustments; therefore, it should not be disturbed unless its accuracy is suspect or repairs dictate that adjustments are necessary.

5.4.2.1 Forward Power Reading: Check the accuracy of the forward power indication of

Power/Mod meter as follows:

TEST-

(a) Set switches as tabulated for Test Setting in

table 4-1.

(b) Verify dummy load has provision to accurately

measure the power output of the transmitter to within 2%.

RF switch to ON.

(d) Adjust

O/P POWER potentiometer A4A2R48

(A5A2R48) for precisely 500 watts (by dummy load's forward power indication).

(e) Set

TEST-Power/Mod switch to REFL PWR.

(f) Indication on

TEST-Power/Mod meter shall be

near zero.

(g) Set

O/P POWER potentiometer A4 (A5) A2R48

for the intended carrier level, as displayed by dummy load's forward power indication.

Page 5-20

15 January 2005

Nautel ND2000A-02x-xx0 Technical Instructions

Specifications and Main Features

Frequently Asked Questions

User Manual