UBS Axcera DT325B Users Manual

INSTRUCTION MANUAL

DT325B

350 Watt Digital VHF

Low Band Transmitter

AXCERA, LLC

103 FREEDOM DRIVE P.O. BOX 525 LAWRENCE, PA 15055-0525 USA

(724) 873-8100 • FAX (724) 873-8105

www.axcera.com • info@axcera.com

350-Watt Digital VHF LB Transmitter Table of Contents

TABLE OF CONTENTS

Section Page CHAPTER 1 INTRODUCTION

1.1 Manual Overview...................................................................................1-1

1.2 Assembly Designation Numbers ..............................................................1-1

1.3 Safety..................................................................................................1-2

1.4 Contact Information...............................................................................1-2

1.5 Material Return Procedure ......................................................................1-2

1.6 Warranty for Axcera Products – Limited One-Year Warranty.......................1-3

CHAPTER 2 SYSTEM DESCRIPTION

2.1 System Overview ..................................................................................2-1

2.2 Exciter Driver Chassis Assembly Description.............................................2-1

2.2.1 Control & Monitoring Power Supply Module Assembly.......................2-2

2.2.2 Upconverter and Downconverter Module.........................................2-2

2.2.3 Adaptive Equalization Circuits........................................................2-3

2.3 VHF Low Band Amplifier Tray..................................................................2-3

2.4 Control and Status.................................................................................2-6

2.4.1 Front Panel Display Screen............................................................2-6

2.5 System Operation..................................................................................2-6

2.5.1 Principals of Operation..................................................................2-6

2.6 Maintenance .........................................................................................2-8

2.6 Module Replacement .......................................................................2-8

2.7 Customer Remote Connections ...............................................................2-9

CHAPTER 3 INSTALLATION AND SETUP PROCEDURES

3.1 Site Considerations................................................................................3-1

3.2 Unpacking and Installation of the Cabinet and Trays .................................3-4

3.3 Input and Output Connections to the Transmitter .....................................3-5

3.3.1 Main AC Connection to the Transmitter System ...............................3-5

3.3.2 Input Connections to the Transmitter System..................................3-5

3.4 Setup and Operation Procedures.............................................................3-7

3.4.1 Driver/Amplifier Modules front panel LEDs ......................................3-7

3.4.1.1 Axciter Upconverter Sled Module front panel LEDs..................3-8

3.4.1.2 Controller Module front panel LEDs .......................................3-8

3.4.2 Front Panel LCD Screen for Driver/Amplifier Chassis Assembly..........3-8

CHAPTER 4 CIRCUIT DESCRIPTIONS

4.1 Control Monitoring/Power Supply Module .................................................4-1

4.1.1 Power Protection Board.................................................................4-1

4.1.2 System Controller Board ...............................................................4-2

4.1.2.1 Schematic Sheet 1 ..............................................................4-2

4.1.2.2 Schematic Sheet 2 ..............................................................4-3

4.1.2.3 Schematic Sheet 3 ..............................................................4-3

4.1.2.4 Schematic Sheet 4 ..............................................................4-3

4.1.2.5 Schematic Sheet 5 ..............................................................4-4

4.1.3 LCD w/Switches Board..................................................................4-4

4.1.4 Switching Power Supply Assembly .................................................4-5

4.1.5 RF Output of Driver/Amplifier Chassis Assembly ..............................4-5

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350-Watt Digital VHF LB Transmitter Table of Contents

TABLE OF CONTENTS (continued)

Section Page

4.2 VHF Low Band Amplifier Tray..................................................................4-5

4.2.1 Phase Shifter Board......................................................................4-6

4.2.2 Filter/Amplifier Board....................................................................4-6

4.2.3 VHF Low Band Amplifier Board.......................................................4-7

4.2.4 Overdrive Protection Board............................................................4-7

4.2.5 3 Way Splitter Board ....................................................................4-7

4.2.6 VHF Low Band Output Amplifier Pallets...........................................4-7

4.2.7 3 Way Combiner ..........................................................................4-8

4.2.8 AGC Control Board .......................................................................4-8

4.2.9 +28 VDC Switching Power Supply..................................................4-9

4.2.10 Current Metering Board...............................................................4-9

4.2.11 Operation of the VHF Amplifier Tray .............................................4-9

4.3 External Boards...................................................................................4-10

4.3.1 Triple Peak Detector Board..........................................................4-10

4.3.2 Isolation Relay Board..................................................................4-11

CHAPTER 5 DETAILED ALIGNMENT PROCEDURES

5.1 System Preparation ...............................................................................5-1

5.2 Module Replacement..............................................................................5-1

5.3 VHF Amplifier Tray.................................................................................5-1

5.3.1 AGC Control Board .......................................................................5-1

5.3.2 Phase Shifter Board......................................................................5-2

5.3.3 Filter/Amplifier Board....................................................................5-2

5.3.4 VHF Low Band Amplifier Board.......................................................5-2

5.3.5 Overdrive Protection Board............................................................5-2

5.3.6 3 Way Splitter Board ....................................................................5-2

5.3.7 VHF Output Amplifier Pallets..........................................................5-2

5.3.8 3 Way Combiner Board.................................................................5-3

5.4 Calibration of the Output Power of the VHF Amplifier Tray .........................5-3

5.5 Setting Up the Output Power of the Transmitter .......................................5-3

5.5.1 Setting Up of AGC 1 .....................................................................5-3

5.5.2 Setting Up of Overdrive Threshold..................................................5-4

5.5.3 Axciter Relay K2 Sample Values.....................................................5-5

5.5.4 Upconverter/Downconverter Adjustment ........................................5-5

5.6 System Calibration of Forward & Reflected Powers using the Driver/

Amplifier LCD Display ............................................................................5-5

5.6.1 Forward Power Calibration.............................................................5-5

5.6.2 Reflected Power Calibration...........................................................5-5

APPENDICES

APPENDIX A DT325B w/AXCITER SYSTEM DRAWINGS APPENDIX B DRIVER/AMPLIFIER CHASSIS ASSEMBLY DRAWINGS APPENDIX C VHF LOW BAND AMPLIFIER TRAY DRAWINGS

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350-Watt Digital VHF LB Transmitter Table of Contents

LIST OF FIGURES

Figure Page

1-1 Brady Marker Identification .............................................................1-1

2-1 Driver/Amplifier Chassis Assembly Front View ...................................2-1

2-2 Rear view Driver/Amplifier Chassis Assembly ....................................2-9

3-1 1 kW Minimum Ventilation Configuration...........................................3-4

3-2 Front and Rear view Driver/Amplifier Chassis Assembly......................3-4

3-3 AC Input Box Assembly...................................................................3-5

3-4 Rear view Driver/Amplifier Chassis Assembly ....................................3-6

5-1 Axciter Upconverter/Downconverter Main Screen...............................5-4

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350-Watt Digital VHF LB Transmitter Table of Contents

LIST OF TABLES

Table Page

2-1 DT325B Assemblies and Trays.........................................................2-1

2-2 Controller/Power Supply Front Panel Display .....................................2-2

2-3 Controller/Power Supply Front Panel Status Indicators .......................2-2

2-4 Controller/Power Supply Front Panel Control Adjustments ..................2-2

2-5 VHF Amplifier Front Panel Tray Control Adjustments ..........................2-4

2-6 VHF Amplifier Tray Sample..............................................................2-4

2-7 VHF Amplifier Tray Switches............................................................2-5

2-8 VHF Amplifier Tray Fault Indicators ..................................................2-6

2-9 (A2) Driver/Amplifier Remote Connections............................... 2-9

3-1 Rear Chassis Connections for Digital Driver/Amplifier Chassis..............3-6

Digital Driver/Amplifier System LCD Controller Screens

3-2 Menu 01 Splash Screen #1..............................................................3-9

3-3 Menu 02 Splash Screen #2..............................................................3-9

3-4 Menu 10 Main Screen ..................................................................3-9

3-5 Menu 11 Error List Screen ............................................................3-9

3-6 Menu 12 Transmitter Device Data Access Screen ..........................3-10

3-7 Menu 13 Transmitter Configuration Access Screen.........................3-10

3-8 Menu 20 Error List Display Screen..................................................3-10

3-9 Menu 30 Transmitter Device Details Screen ....................................3-10

3-10 Menu 30-1 System Details Screen..................................................3-11

3-11 Transmitter Device Parameters Detail Screens Table........................3-11

3-12 Menu 40 Authorized Personnel Screen............................................3-12

3-13 Menu 40-1 Transmitter Set-Up: Power Control Screen......................3-12

3-14 Menu 40-2 Transmitter Set-Up: Model Select Screen .......................3-13

3-15 Menu 40-3 Transmitter Set-Up: Upconverter Channel Select Screen..3-13

3-16 Menu 40-5 Transmitter Set-Up: Serial Address Screen.....................3-13

3-17 Menu 40-6 Transmitter Set-Up: System Forward Power Calibration ...3-13 3-18 Menu 40-9 Transmitter Set-Up: System Reflected Power Calibration..3-13 3-19 Menu 40-13 Transmitter Set-Up: Min Forward Power Fault Threshold 3-14 3-20 Menu 40-14 Transmitter Set-Up: Max Reflected Pwr Fault Threshold .3-14 3-21 Menu 40-19 Transmitter Set-Up: Remote Commands Control Screen.3-14

4-1 Innovator DIP Switch Settings for SW2.............................................4-3

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350-Watt VHF LB Digital Transmitter Chapter 1, Introduction

Chapter 1

Introduction

This manual explains the installation, setup, alignment, and maintenance procedures for the DT325B 350-watt digital VHF low band transmitter. It is important that you read all of the instructions, especially the safety information in this chapter, before you begin to install or operate the unit.

1.1 Manual Overview This instruction manual is divided into

five chapters and supporting appendices. Chapter 1, Introduction, contains information on safety, the Axcera method of assigning assembly designation numbers, maintenance, return procedures, and warranties. Chapter 2 describes the transmitter and its system control and status indicators and remote control connections. Chapter 3 explains how to unpack, install, set up, and operate the transmitter. Chapter 4, Circuit Descriptions, describes the circuits that make up the trays and assemblies in the transmitter. Chapter 5, Detailed Alignment Procedures, provides information on adjusting the system assemblies for optimal operation. Appendix A contains the system specifications sheet. Appendix B contains the system drawings and parts lists. Appendix C contains the assembly and subassembly drawings and parts lists for the exciter/driver chassis and modules. Appendix D contains the drawings and parts lists for the VHF Low Band Amplifier Tray and the assemblies and subassemblies that make up the tray.

1.2 Assembly Designation Numbers

Axcera has assigned assembly numbers, Ax designations such as A1, where x=1,2,3…etc, to all assemblies, modules, and boards in the system. These designations are referenced in the text of this manual and shown on the block

diagrams and interconnect drawings provided in the appendices. The Block Diagrams, Interconnects, Schematics, Assembly Drawings and Parts Lists are arranged in increasing numerical order in the appendices. Section titles in the text for assembly or module descriptions or alignment procedures contain the associated part number(s) and the relevant appendix that contains the drawings for that item.

The cables that connect between the boards within a tray or assembly and that connect between the trays, racks and cabinets are labeled using Brady markers.

Figure 1-1 is an example of a Brady marked cable. There may be as few as two or as many as four Markers on any one cable. These Brady markers are read starting furthest from the connector. If there are four Brady Markers, this marker is the transmitter number such as transmitter 1 or transmitter 2. The next or the furthest Brady Marker is the rack or cabinet number on an interconnect cable or the board number within a tray. The next number on an interconnect cable is the Tray location or number. The Brady marker closest to the connector is the jack or connector number on an interconnect cable or the jack or connector number on the board within a tray.

Figure 1-1 Brady Marker Identification

Drawing

1.3 Safety

The DT325B transmitters manufactured by Axcera are designed to be easy to use

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350-Watt VHF LB Digital Transmitter Chapter 1, Introduction

and repair while providing protection from electrical and mechanical hazards. Listed throughout the manual are notes, cautions, and warnings concerning possible safety hazards that may be encountered while operating or servicing the transmitter. Please review these warnings and familiarize yourself with the operation and servicing procedures before working on the transmitter.

Read All Instructions – All of the operating and safety instructions should be read and understood before operating this equipment.

Retain Manuals – The manuals for the transmitter should be retained at the transmitter site for future reference. We provide two sets of manuals for this purpose; one set can be left at the office while one set can be kept at the site.

Heed Notes, Warnings, and Cautions – All of the notes, warnings,

and cautions listed in this safety section and throughout the manual must be followed.

Follow Instructions – All of the operating and use instructions for the transmitter should be followed.

Cleaning – Unplug or otherwise disconnect power from the equipment before cleaning. Do not use liquid or aerosol cleaners. Use a damp cloth for cleaning.

Ventilation – Openings in the cabinets and tray front panels are provided for ventilation. To ensure reliable operation, and to protect the unit from overheating, these openings must not be blocked.

Servicing – Do not attempt to service this product until becoming familiar with the equipment. If in doubt, refer all servicing questions to qualified Axcera service personnel.

Replacement Parts – When replacement parts are used, be sure that

the parts have the same functional and performance characteristics as the original part. Unauthorized substitutions may result in fire, electric shock, or other hazards. Please contact the Axcera Technical Service Department if you have any questions regarding service or replacement parts.

1.4 Contact Information

The Axcera Field Service Department can be contacted by phone at 1-724-873- 8100 or by fax at 1-724-873-8105.

Before calling Axcera, please be prepared to supply the Axcera technician with answers to the following questions. This will save time and help ensure the most direct resolution to the problem.

1. What are the Customers’ Name and call letters?

2. What are the model number and type of transmitter?

3. Is the transmitter digital or analog?

4. How long has the transmitter been on the air? (Approximately when was the transmitter installed).

5. What are the symptoms being exhibited by the transmitter? Include the current front panel meter readings and the status of LEDs on the front panels of the trays. If possible, include the meter readings before the problem occurred.

1.5 Material Return Procedure

To insure the efficient handling of equipment or components that have been returned for repair, Axcera requests that each returned item be accompanied by a Return Material Authorization Number (RMA#).

The RMA# can be obtained from any Axcera field service engineer by calling the Axcera Field Service Department at 1724-873-8100. This procedure applies to

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350-Watt VHF LB Digital Transmitter Chapter 1, Introduction

all items sent to the Field Service Department regardless of whether the item was originally manufactured by Axcera.

When equipment is sent to the field on loan, the RMA# is included with the unit. The RMA# is intended to be used for the return of the unit to Axcera. In addition, all shipping material should be retained for the return of the unit to Axcera. Replacement assemblies are also sent with the RMA# to allow for the proper routing of the exchanged hardware.

Failure to close out this type of RMA# will normally result in the customer being invoiced for the value of the loaner item or the exchange assembly.

When shipping an item to Axcera, please include the RMA# on the packing list and on the Axcera-provided shipping container. The packing slip should also include contact information and a brief description of why the unit is being returned.

Please forward all RMA items to:

Axcera 103 Freedom Drive P.O. Box 525 Lawrence, PA 15055-0525 USA

For more information concerning this procedure, call Axcera Field Service at

1-724-873-8100 or by fax at 1-724-873-8105.

Axcera can also be contacted through email at info@axcera.com and on the Web at www.axcera.com.

1.6 Warranty for Axcera Products – Limited One-Year Warranty

Axcera warrants each new product that it has manufactured and sold against defects in material and workmanship under normal use and service for a period of one (1) year from the date of

shipment from Axcera's plant, when operated in accordance with Axcera's operating instructions. This warranty shall not apply to tubes, fuses, batteries, or bulbs.

Warranties are valid only when and if (a) Axcera receives prompt written notice of breach within the period of warranty, (b) the defective product is properly packed and returned by the buyer (transportation and insurance prepaid), and (c) Axcera determines, in its sole judgment, that the product is defective and not subject to any misuse, neglect, improper installation, negligence, accident, or (unless authorized in writing by Axcera) repair or alteration. Axcera’s exclusive liability for any personal and/or property damage (including direct, consequential, or incidental) caused by the breach of any or all warranties, shall be limited to the following: (a) repairing or replacing (in Axcera's sole discretion) any defective parts free of charge (F.O.B. Axcera's plant) and/or (b) crediting (in Axcera's sole discretion) all or a portion of the purchase price to the buyer.

Equipment furnished by Axcera, but not bearing its trade name, shall bear no warranties other than the special hoursof-use or other warranties extended by or enforceable against the manufacturer at the time of delivery to the buyer.

NO WARRANTIES, WHETHER STATUTORY, EXPRESSED, OR IMPLIED, AND NO WARRANTIES OF MERCHANTABILITY, FITNESS FOR ANY PARTICULAR PURPOSE, OR FREEDOM FROM INFRINGEMENT, OR THE LIKE, OTHER THAN AS SPECIFIED IN PATENT LIABILITY ARTICLES, AND IN THIS ARTICLE, SHALL APPLY TO THE EQUIPMENT FURNISHED HEREUNDER.

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350-Watt VHF LB Digital Transmitter Chapter 1, Introduction

F WARNING!!!

× HIGH VOLTAGE Ø

DO NOT ATTEMPT TO REPAIR OR TROUBLESHOOT THIS EQUIPMENT UNLESS YOU ARE FAMILIAR WITH ITS OPERATION AND EXPERIENCED IN SERVICING HIGH VOLTAGE EQUIPMENT. LETHAL VOLTAGES ARE PRESENT WHEN POWER IS APPLIED TO THIS SYSTEM. IF POSSIBLE, TURN OFF POWER BEFORE MAKING ADJUSTMENTS TO THE SYSTEM.

« RADIO FREQUENCY RADIATION HAZARD «

MICROWAVE, RF AMPLIFIERS AND TUBES GENERATE HAZARDOUS RF RADIATION THAT CAN CAUSE SEVERE INJURY INCLUDING CATARACTS, WHICH CAN RESULT IN BLINDNESS. SOME CARDIAC PACEMAKERS MAY BE AFFECTED BY THE RF ENERGY EMITTED BY RF AND MICROWAVE AMPLIFIERS. NEVER OPERATE THE TRANSMITTER SYSTEM WITHOUT A PROPERLY MATCHED RF ENERGY ABSORBING LOAD ATTACHED. KEEP PERSONNEL AWAY FROM OPEN WAVEGUIDES AND ANTENNAS. NEVER LOOK INTO AN OPEN WAVEGUIDE OR ANTENNA. MONITOR ALL PARTS OF THE RF SYSTEM FOR RADIATION LEAKAGE AT REGULAR INTERVALS.

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350-Watt VHF LB Digital Transmitter Chapter 1, Introduction

EMERGENCY FIRST AID INSTRUCTIONS

Personnel engaged in the installation, operation, or maintenance of this equipment are urged to become familiar with the following rules both in theory and practice. It is the duty of all operating personnel to be prepared to give adequate Emergency First Aid and thereby prevent avoidable loss of life.

RESCUE BREATHING

1. Find out if the person is breathing.

You must find out if the person has stopped breathing. If you think he is not breathing, place him flat on his back. Put your ear close to his mouth and look at his chest. If he is breathing you can feel the air on your cheek. You can see his chest move up and down. If you do not feel the air or see the chest move, he is not breathing.

2. If he is not breathing, open the airway by tilting his head backwards.

Lift up his neck with one hand and push down on his forehead with the other. This opens the airway. Sometimes doing this will let the person breathe again by himself.

3. If he is still not breathing, begin rescue breathing.

-Keep his head tilted backward. Pinch nose shut.

-Put your mouth tightly over his mouth.

-Blow into his mouth once every five seconds

-DO NOT STOP rescue breathing until help arrives.

LOOSEN CLOTHING - KEEP WARM

Do this when the victim is breathing by himself or help is available. Keep him as quiet as possible and from becoming chilled. Otherwise treat him for shock.

BURNS

SKIN REDDENED: Apply ice cold water to burned

area to prevent burn from going deeper into skin tissue. Cover area with a clean sheet or cloth to keep away air. Consult a physician.

SKIN BLISTERED OR FLESH CHARRED: Apply ice cold water to burned area to prevent burn from going deeper into skin tissue.

DT325B, Rev. 0 1-5

Cover area with clean sheet or cloth to keep away air. Treat victim for shock and take to hospital.

EXTENSIVE BURN - SKIN BROKEN: Cover area with clean sheet or cloth to keep away air. Treat victim for shock and take to hospital.

350-Watt VHF LB Digital Transmitter Chapter 1, Introduction

dBm, dBw, dBmV, dBµV, & VOLTAGE

EXPRESSED IN WATTS

50 Ohm System

WATTS PREFIX dBm dBw dBmV dBµV VOLTAGE 1,000,000,000,000 1 TERAWATT +150 +120 100,000,000,000 100 GIGAWATTS +140 +110 10,000,000,000 10 GIGAWATTS +130 +100 1,000,000,000 1 GIGAWATT +120 + 99 100,000,000 100 MEGAWATTS +110 + 80 10,000,000 10 MEGAWATTS +100 + 70 1,000,000 1 MEGAWATT + 90 + 60 100,000 100 KILOWATTS + 80 + 50 10,000 10 KILOWATTS + 70 + 40 1,000 1 KILOWATT + 60 + 30 100 1 HECTROWATT + 50 + 20 50 + 47 + 17 20 + 43 + 13 10 1 DECAWATT + 40 + 10 1 1 WATT + 30 0 + 77 +137 7.07V

0.1 1 DECIWATT + 20 - 10 + 67 +127 2.24V

0.01 1 CENTIWATT + 10 - 20 + 57 +117 0.707V

0.001 1 MILLIWATT 0 - 30 + 47 +107 224mV

0.0001 100 MICROWATTS - 10 - 40

0.00001 10 MICROWATTS - 20 - 50

0.000001 1 MICROWATT - 30 - 60

0.0000001 100 NANOWATTS - 40 - 70

0.00000001 10 NANOWATTS - 50 - 80

0.000000001 1 NANOWATT - 60 - 90

0.0000000001 100 PICOWATTS - 70 -100

0.00000000001 10 PICOWATTS - 80 -110

0.000000000001 1 PICOWATT - 90 -120

TEMPERATURE CONVERSION

°F = 32 + [(9/5) °C]

°C = [(5/9) (°F - 32)]

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350-Watt VHF LB Digital Transmitter Chapter 1, Introduction

USEFUL CONVERSION FACTORS

TO CONVERT FROM TO MULTIPLY BY

mile (US statute) kilometer (km) 1.609347 inch (in) millimeter (mm) 25.4 inch (in) centimeter (cm) 2.54 inch (in) meter (m) 0.0254 foot (ft) meter (m) 0.3048 yard (yd) meter (m) 0.9144 mile per hour (mph) kilometer per hour(km/hr) 1.60934 mile per hour (mph) meter per second (m/s) 0.44704 pound (lb) kilogram (kg) 0.4535924 gallon (gal) liter 3.7854118 U.S. liquid (One U.S. gallon equals 0.8327 Canadian gallon) fluid ounce (fl oz) milliliters (ml) 29.57353 British Thermal Unit watt (W) 0.2930711 per hour (Btu/hr) horsepower (hp) watt (W) 746

NOMENCLATURE OF FREQUENCY BANDS

FREQUENCY RANGE DESIGNATION 3 to 30 kHz VLF - Very Low Frequency

30 to 300 kHz LF - Low Frequency 300 to 3000 kHz MF - Medium Frequency 3 to 30 MHz HF - High Frequency 30 to 300 MHz VHF - Very High Frequency 300 to 3000 MHz UHF - Ultrahigh Frequency 3 to 30 GHz SHF - Superhigh Frequency 30 to 300 GHz EHF - Extremely High Frequency

LETTER DESIGNATIONS FOR UPPER FREQUENCY

BANDS

LETTER FREQ. BAND

L 1000 - 2000 MHz S 2000 - 4000 MHz C 4000 - 8000 MHz X 8000 - 12000 MHz Ku 12 - 18 GHz K 18 - 27 GHz Ka 27 - 40 GHz V 40 - 75 GHz W 75 - 110 GHz

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350-Watt VHF LB Digital Transmitter Chapter 1, Introduction

0 -10 -20 -30 -40 -50 -60

-70

RETURN LOSS VS. VSWR

R E T U R

L O S S

1.001 1.01 1.1 2.0

VSWR

DT325B, Rev. 0 1-8

350-Watt VHF LB Digital Transmitter Chapter 1, Introduction

ABBREVIATIONS/ACRONYMS

AC Alternating Current AFC Automatic Frequency Control ALC Automatic Level Control AM Amplitude modulation AGC Automatic Gain Control AWG American wire gauge BER Bit Error Rate BW Bandwidth DC Direct Current D/A Digital to analog dB Decibel dBm Decibel referenced to

1 milliwatt dBmV Decibel referenced to

1 millivolt

dBw Decibel referenced to 1 watt FEC Forward Error Correction

FM Frequency modulation Hz Hertz ICPM Incidental Carrier Phase

Modulation I/P Input IF Intermediate Frequency LED Light emitting diode LSB Lower Sideband MPEG Motion Pictures Expert Group O/P Output PLL Phase Locked Loop PCB Printed circuit board QAM Quadrature Amplitude

Modulation

DT325B, Rev. 0 1-9

350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance &

A1 A5

Remote Control Connections

Chapter 2

System Description, Maintenance and Remote Control Connections

Figure 2-1: Driver/Amplifier Chassis Assembly

Table 2-1: DT325B Major Assemblies and Trays

ASSEMBLY

DESIGNATION

TRAY/ASSEMBLY NAME ASSEMBLY NUMBER

A24 Axciter Modulator 1305842

Driver/Amplifier Chassis Assembly

A2-A11 Backplane Board 1310080

A2-A1 Downconverter Module 1311157 A2-A5 Upconverter Module 1310226 A2-A4 Control/Power Supply Module 1310835 (220 VAC)

A3 VHF Low Band Amplifier Tray 1304363

2.1 System Overview

The DT325B is a complete VHF low band solid-state digital television transmitter that operates at a nominal average output power of 350 watts.

The transmitter needs an AC input line of 220 VAC at 40 amps that connects to the AC Distribution Panel which distributes the AC through AC power cords to the VHF exciter/driver chassis and the VHF amplifier tray.

The DT325B consists of (A24) an Axciter Modulator Tray, (A2) a Driver/Amplifier Chassis Assembly and (A3) a VHF Low Band Amplifier Tray. The assemblies and trays are listed in Table 2-1.

1310206

2.2: Exciter Driver Chassis Assembly, LXB, 220 VAC (1310206; Appendix C)

The chassis assembly is factory set for operation using 220 VAC. All of the modules, except the power amplifier module and the power supply section of the Control & Monitoring/Power Supply Module, plug directly into a backplane board. The backplane board (1310080) provides module to module interconnection as well as interconnection to remote command and control connectors.

NOTE: Information and drawings on the Axciter Modulator Tray (1305842) and the Upconverter Module (1310226) and Downconverter Module (1311157) are found in the separate Axciter Manual.

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350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance & Remote Control Connections

2.2.1: (A4) Exciter Control/ Power Supply Assembly, LXB, 220VAC (1310835; Appendix C)

The (A4) Control/Power Supply Assembly is made up of a System Controller Board (1310089), a Power Protection Board (1302837) and a LCD

Table 2-2: Controller/Power Supply Display

DISPLAY FUNCTION

A 4 x 20 display providing a four-line readout of the internal

LCD

Table 2-3: Controller/Power Supply Status Indicator

LED FUNCTION

OPERATE

( green )

FAULT

( red or green )

DC OK

( red or green )

Table 2-4: Controller/Power Supply Control Adjustments

POTENTIOMETER DESCRIPTION

DISPLAY CONTRAST Adjusts the contrast of the display for desired viewing of screen.

2.2.2: (A5) Upconverter Module (1310226) and (A1) Downconverter Module (1311157)

NOTE: More information and the drawings on the Axciter Modulator Tray (1305842) and the Upconverter Module (1310226) and Downconverter Module (1311157) are found in the separate Axciter Manual.

The output from the Axciter modulator, which is an 8-VSB IF signal centered at 44 MHz. that is -6 dBm in level, is cabled to J68 on the rear panel of the

functions, external inputs, and status. See Chapter 3, Controller/Power Supply Display Screens, for a listing of displays.

When lit it indicates that the transmitter is in the Operate Mode. If transmitter is Muted the Operate LED will stay lit, the transmitter will remain in Operate, until the input signal is returned. Red indicates that a problem has occurred in the transmitter. The transmitter will be Muted or placed in Standby until the problem is corrected. Green indicates that the switchable fuse protected DC outputs that connect to the modules in the transmitter are OK.

w/Switches Board (1307977). The Assembly also contains a switching power supply that provides ±12 VDC to the rest of the modules in the chassis and +32 VDC to the Power Amplifier module if needed.

The Assembly provides all transmitter control and monitoring functions. The Front panel LCD allows monitoring of system parameters, including forward and reflected power, transistor currents, module temperatures and power supply voltages.

Driver/Amplifier Chassis Assembly. The IF input is connected to the upconverter module assembly through the backplane board in the chassis assembly. The 44 MHz IF signal is upconverted to the desired channel frequency by the upconverter module. The resulting RF signal is amplified and wired to a Pin Diode Attenuator which adjusts the gain of the module that is controlled by an Automatic Gain Control circuit. The AGC maintains a constant power out of the upconverter, and also the transmitter, that connects to the power amplifier module. The gain controlled output of the

DT325B, Rev. 0 2-2

350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance &

Remote Control Connections pin diode circuit is connected to the

output of the Upconverter Module, approximately +10 dBm in level, at J23, on the rear panel of the Driver/Amplifier Chassis Assembly. This output is cabled to the (A10) splitter and then the VHF amplifier tray in the system.

2.2.3: Adaptive Equalization Circuits

The adaptive equalization circuits for the system are contained in the Axciter Modulator which controls the K2 relay whose output connects to the downconverter module mounted in the Driver/Amplifier Chassis Assembly. Two transmitter output samples are taken from directional couplers located before, pre-filter, and after the channel mask filter, post-filter, that are applied to the external K2 Relay. The switching of the relay between the pre and post filter samples is controlled by the Axciter Modulator through J7 on the rear panel of the tray.

The pre or post filter sample is connected to J12 the Downconverter RF input jack located on the on the rear panel of the Driver/Amplifier Chassis Assembly. The downconverted IF transmitter sample output of the downconverter module at J13, on the rear panel of the Driver/Amplifier Chassis Assembly, is cabled to J2 on the Axciter Modulator.

The signal is digitized by the Axciter modulator and demodulated in non-real time software. The result is analyzed to calculate linear and nonlinear adaptive equalizers to improve the transmitted signal quality by compensating for the nonlinear compression of the power amplifier, and the linear distortions (mostly group delay effects) of the channel filter.

When a linear adaptive equalizer is being calculated, the transmitter sample is taken after the channel mask filter so that its linear distortions can be “seen.”

When a nonlinear adaptive equalizer is being calculated, the transmitter sample is taken before the channel mask filter, so

that the distortion sidebands being generated by the power amplifier can be seen (the channel filter would remove the out-of-band sidebands).

The Axciter modulator contains a standard Personal Computer. The PC performs user interface functions and the numerical processing necessary for the adaptive linear and nonlinear equalization. The PC is not in the forward signal path; if it fails the exciter will continue to generate a signal with the most recently calculated equalization.

2.3: VHF Low Band Amplifier Tray (1304363; Appendix D)

The tray provides approximately 54 dB of gain. The tray contains (A1-A1) the phase shifter board 1198-1602 and (A1-A2) the Filter/amplifier board 1198-1606, which are mounted in the (A1) RF enclosure assembly. The (A2-A1) VHF low band amplifier board 1198-1605, the (A2-A2) Overdrive protection board 1198-1601 and the (A2-A3) 3-way splitter board 11981608, which are mounted in the (A2) RF enclosure assembly. The (A3-A1, A3-A2 and A3-A3) low band VHF amplifier pallets, P400-VHF-L-18, 1304348 which are mounted in the (A3) RF enclosure assembly. The (A4-A1) 3-way combiner board 1198-1626 and the (A4-A2 & A4A3) Low pass filter boards 1198-1628, which are mounted in the (A4) 3 way combiner enclosure. The tray also contains the (A5) AGC control board 1306482, the (A8) Current metering board 1304362 and (A10) the +30 VDC switching power supply assembly PM3329B-5-1-R-2-E, 1301504.

The On Channel RF signal (0 to +10 dBm), enters the rear of the Tray at the "BNC" Jack J1. The RF connects to a phase shifter board that provides a phase shift adjustment of the RF Signal that is needed to produce the maximum output during the combining of multiple Amplifier Trays in an Amplifier Array. The output of the phase shifter is cabled to the filter/amplifier board. The gain of the tray

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350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance &

Remote Control Connections is controlled by an external bias voltage

that connects to the AGC Control Board and adjusts the AGC Pin Attenuator Bias Voltage which is applied to the Filter/Amplifier Board. The RF output of the Filter/Amplifier Board is amplified by the LB Amplifier Board and connected to the Overdrive Protection Board. The overdrive protection board provides a trip point, 110%, for over power conditions which will cut back the output power of the Tray.

The RF Output of the Overdrive Protection Board connects to the 3 Way Splitter Board. The three RF outputs connect to the three Low Band Output Amplifier Pallets. Each amplifier pallet provides approximately 18 dB gain. The RF signal inputs to the Output Amplifier Boards (+33.3 dBm) are amplified to +51.3 dBm outputs at J2, which are connected to the 3 Way Combiner Assembly. The 3 Way Combiner takes the three +51.3 dBm combined inputs and combines them to form the ˜375 Watt RF Output at J4 of the Combiner which soldered to J2, the RF Output Jack of the Tray.

The 3 Way Combiner Board provides a Forward Power Sample and a Reflected Output Power Sample that connect thru low pass filters to the AGC Control Board. The AGC Control Board provides detected outputs that are used for front panel and remote meter Indications of the forward and reflected output power levels, AGC

Table 2-5: VHF Amplifier Tray Control Adjustments

ADJUSTMENT DESCRIPTION

R2 – A7

Phase

R3 – A6

Gain

Table 2-6: VHF Amplifier Tray Sample

SAMPLE DESCRIPTION

RF Front Panel Sample

Adjusts the phase of the RF output by approximately 70°. Adjusts the gain of the RF output when the amplifier control

board is in the AGC mode.

Forward power sample of the tray from the AGC control board.

Detector Voltage Level and also the VSWR Cutback protection if the Reflected Power level increases above the preset level.

Two voltages, +28 VDC from the internal switching power supply and +12 VDC from the Driver/Amplifier Assembly are needed for operation of the Tray. The +12 VDC is connected to a +5 VDC Regulator IC which supplies the +5 VDC needed for operation of the front panel mounted LEDs. The (A10) +28 VDC Switching Power Supply provides the +28 VDC to the Current Metering Board. The Current Metering Board distributes the voltages through fuses to the Amplifier Devices on the Filter/Amplifier, Low Band Driver Board and the three Final Low Band Amplifier Boards.

The Current Metering Board also supplies sample outputs of the operating currents of the amplifier devices in the Tray to the front panel Current Meter. The Meter in the (I1) position reads the current for the (A3-A1) Low Band Output Amplifier Board, (I2) for the (A3-A2) Low Band Output Amplifier Board and (I3) for the (A3-A3) Low Band Output Amplifier Board. To read the desired current; switch S2 to the proper position checking that S1 is in the Current position. These current readings can be used when setting up the Idling Currents, no RF Drive applied, for the devices. (I1, I2 & I3) are set for 3 Amps max.

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Table 2-7: VHF Amplifier Tray Switches

SWITCH FUNCTION

CB1

On/Off Circuit Breaker

Switch, Meter

Switches 220 VAC through a 15-amp circuit breaker-type protection device. The switch lights if AC is present. The AC is applied to the switching power supply in the tray.

Selects the desired % Forward Output Power, % Reflected Power reading, AGC Voltage, Power Supply Voltage, or Current

With Switch S1 in

Position

Reads the % Forward Output

% Forward

% Refl (Reflected)

AGC Voltage

Power Supply

Current

Selects the current of the transistor devices on the low band amplifier boards. S1 must be in the Current position.

With Switch S2 in

Position

Power of the tray (100%= 375 watts DTV) Reads the % Reflected Output Power (<5%) Reads the AGC level of the tray (1 to 3 VDC) Reads the voltage from the switching power supply (+28 VDC) Uses Switch S2 to indicate the current of transistor devices

Reads the current of (A3-A1) the low band amplifier board (idling current=1.8 amps and operating current=12-13 amps, black picture)

Display

Switch, Meter

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Reads the current of (A3-A2) the low band amplifier board (idling current=1.8 amps and operating current=12-13 amps, black picture) Reads the current of (A3-A3) the low band amplifier board (idling current=1.8 amps and operating current=12-13 amps, black picture) Reads the current of (A2-A1) the low band amplifier board (idling current=3 amps and operating current=3 amps, black picture)

350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance & Remote Control Connections

Table 2-8: VHF Amplifier Tray Fault Indicators

INDICATOR DESCRIPTION

DS1

Overdrive

DS2

Enable

DS3

Module Status

DS4

VSWR Cutback

DS5

Overtemperature

2.4: Control and Status The control and status of the

exciter/amplifier chassis assembly is found by operating the front panel display screen on the assembly. Detailed information on the use of the screen is found in Chapter 3 of this manual.

2.4.1: Front Panel Display Screen

A 4 x 20 display located on the front of the Control & Monitoring/Power Supply Module is used in the transmitter for control of the operation and display of the operating parameters of the transmitter.

2.5: System Operation

When the transmitter is in operate, as set by the menu screen located on the Control & Monitoring Module, the +32 VDC stage of the Power Supply in the Control & Monitoring Module is enabled, the operate indicator on the front panel is lit and the DC OK on the front panel should also be green. The enable and DC OK indicators on the PA Module will also be turned to green.

When the transmitter is in standby, the IF Processor will be disabled and the mute indicator on the front panel will be red. Also, the +32 VDC stage of the Power Supply in the Control & Monitoring

Indicates that the level of drive is too high. The protection circuit will limit the drive level to the set threshold. The fault is generated on the overdrive protection board. Indicates that the Enable supplied by the driver/amplifier chassis assembly is present Indicates that the forward power sample level is lower than

the set reference level Indicates that the reflected level of the tray has increased above 20%; this will automatically cut back the output power of the tray. The fault is generated on the AGC control board. Indicates that the temperature of (A13, A14 or A15) one of the thermal switches is above 175° F. When this fault occurs, the Enable to the switching power supply is immediately removed.

Module is disabled, the operate indicator on the front panel will be extinguished and the DC OK on the front panel should remain green. The enable and indicator on the PA Module is also extinguished.

If the transmitter does not switch to Operate when the operate menu is switched to Operate, check that all faults are cleared and that the remote control terminal block stand-by signal is not active. Also check that a jumper or external closed interlock is connected from J30-5 to J30-15 on the rear of the exciter/deriver chassis assembly.

2.5.1: Principles of Operation

Operating Modes This transmitter is either operating or in

standby mode. The sections below discuss the characteristics of each of these modes.

Operate Mode

Operate mode is the normal mode for the transmitter when it is providing RF power output. To provide RF power to the output, the transmitter will not be in mute. Mute is a special case of the operate mode where the power supply's 32 VDC section is enabled but there is no RF output power, because of a fault condition that causes the firmware to

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