Crescend Technologies VHFP15XXFF1 Users Manual

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INSTALLATION AND SERVICE

MANUAL

CONTINUOUS DUTY

VHF POWER AMPLIFIER

August 10, 2007 Rev B

Crescend Technologies 920 E. State Parkway Schaumburg, IL 60173

Tel: 847 908 5400 Fax: 847 908 5408 Email: sales@CrescendTech.com Web Site: www.CrescendTech.com

GENERAL DESCRIPTION

Warning! Changes or modifications not expressly approved by the party

responsible for compliance could void the users’ authority to operate the equipment.

Compliance

subject to the following two conditions: (1) This device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.

1.1. INTRODUCTION

This manual contains information and procedures for installation, operation, and general maintenance of Crescend’s VHF Continuous Duty Power Amplifier.

1.2. PRODUCT DESCRIPTION

The Crescend Technologies VHF RF power amplifiers are designed for trunking and conventional repeater applications. Rack mountable and designed to accept a range of input powers for a given rated output power, the amplifier covers a broad range of frequencies. Closed loop power control is used to maintain a constant output power under varying voltage, signal input, frequency and output load conditions. Several design features work to protect the amplifier under adverse conditions.

The amplifier front panel includes status LED indicators for DC and Alarm conditions. RF Input, RF Output, DC, summary alarm and power cutback connections are found on the back of the amplifier. A fan is used to cool the amplifier.

Table 1-1. Amplifier Functional Specifications

Frequency Range: See Table 1-2 (Range Set at Factory) Operating Voltage: +13.8 ±0.7 Vdc Current Consumption: See Table 1-2 Duty Cycle: 100% Power Input: See Table 1-2 (Range Set at Factory) Power Output (Single Carrier Operation): See Table 1-2 (Range Set at Factory) Input Return Loss: -10 dB (Maximum) Spurious & Harmonics: See Table 1-2 Input/Output Impedance: 50 Ohms (Nominal) Load VSWR Tolerance: VSWR Protected above 2.5:1 (Nominal) Input/Output Connector: Type N Female Vertical Mounting: 7.0 in Horizontal Mounting: 19.0 in Weight: 10 lbs (4.6 kg) (Nominal) Cooling Method: Fan Forced Air Over Heat Sink Operating Temp. Range: -30°C to +60 °C Storage & Transport: -40 °C to +70 °C Humidity: 80% at +40 °C (Non-Condensing) Altitude: 10,000 Feet (Maximum)

Front Panel Display:

This device complies with part 15 of the FCC rules. Operation is

INDICATORS

Alarm and Control Pins:

DC ON (Green), LOW OUTPUT (Red), HIGH VSWR (Red), OVER TEMP (Red)

SUMMARY ALARM

Summary of Low Output, High VSWR, Over Temp Alarms

CONTROLS

CTRL(Partial Power Cutback) SH/D (External Power Control)

Table 1-2. Frequency Ranges, Input/Output Power, Current, Spurious and Harmonics

Typ

Frequency

Range (MHz)

136-144 (DA) 144-152 (DB) 152-162 (EA) 162-174 (EB)

NOTES:

All specifications above apply at +13.8 ± 0.1 VDC operating

Input Power

Range (W)

0.1-0.2

0.2-0.5

0.5-1 1-2 2-5

5-10 10-20 20-50

Manufacturer’s Rated Output Power of this Equipment is for Single Carrier Operation.

voltage, ambient temperature of 25°C ± 5°C.

Rated Output

Power (W)

80 (P8) 100 (P10) 110 (P11) 150 (P15)

Current

(A)

16 18 22 26

Max

Current

(A)

19 23 25 28

Spurious

and

Harmonic

s (dBc)

-65 <-65 <

-65 <-67

2. INSTALLATION

2.1. INTRODUCTION

This section contains installation recommendations, unpacking, inspection, and in stallation instructions for the amplifier. Carefully read all the material in this section prior to equipment unpacking or installation. Also read and review the operating procedures in Section 3 prior to installing the equipment. It is important that the licensee perform these tasks correctly and in good faith. If applicable, carefully read Parts 73 and 74 of the Federal Communications Commission (FCC) rules to determine how they apply to your installation.

2.2. ELECTRICAL SERVICE RECOMMENDATIONS

Crescend Technologies recommends that proper AC line conditioning and surge suppression be provided on the primary AC input to the +13.8 VDC power source. All electrical service should be installed in accordance with the National Electrical Code, any applicable state or local codes, and good engineering practice. Special consideration should be given to lightning protection of all systems in view of the vulnerability of most transmitter sites to lightning. Lightning arrestors are recommended in the service entrance. Straight, short ground runs are recommended. The electrical service must be well grounded. Each amplifier should have its own circuit breaker.

2.3. UNPACKING AND INSPECTION

This equipment has been operated, tested and calibrated at the factory. Only in the event of severe mechanical shocks or other mistreatment should any substantial readjustment be required. Carefully open the container(s) and remove the amplifier module(s). Retain all packing material that can be reassembled in the event that the unit must be returned to the factory.

CAUTION:

Visually inspect the amplifier module for damage that may have occurred during shipment. Check for evidence of water damage, bent or warped chassi s, loose screws or nuts, or extraneous packing material in the connector or fans. Inspect the rear panel connector fo r bent connector pins. If the equipment is damaged, a claim should be filed with the carrier once the extent of any damage is assessed. We cannot stress too strongly the importance of IMMEDIATE careful inspection of the equipment and the subsequent IMMEDIATE filing of the necessary claims against the carrier if necessary. If possible, inspect the equipment in the presence of the delivery person. If the equipment is damaged, the carrier is your first area of recourse. If the equipment is damaged and must be returned to the factory, write or phone for a return authorization. Crescend may not accept returns without a return authorization. Claims for loss or damage may not be withheld from any payment to Crescend, nor may any payment due be withheld pending the outcome thereof. WE CANNOT GUARANTEE THE FREIGHT CARRIER’S PERFORMANCE.

2.4. INSTALLATION INSTRUCTIONS

This amplifier is designed for installation in a rack that permits access for connection of DC power, RF, and monitor/control cables. The amplifier must have a minimum of 3 inches of open space to the rear to allow adequate ventilation.

To install the amplifier proceed as follows:

1. Install amplifier in equipment rack and secure in place.

2. Connect a 50 ohm antenna cable and load to the RF OUT connector on rear of amplifier.

3. Connect the transceiver/exciter output to RF IN connector on rear of amplifier.

4. If monitoring of PA is desired, connect alarm cable to “ALARM” pin on rear of

Exercise care in handling equipment during inspection to prevent damage caused by rough or careless handling.

to the rear of the rack

amplifier module. See section 2.5 for more details.

5. If limited output power control of PA is desired, connect control cable or appropriate resistor to “SH/D” pin on rear of amplifier module. See section 2.5 for more details.

6. If remote output power cutback of PA is desired, connect control cable to “CTRL” pin on rear of amplifier module. See section 2.5 for more details.

7. Measure primary DC input voltage. DC input voltage should be +13.8 +/- 0.1VDC. Turn off DC voltage.

WARNING: Turn off external primary DC power before connecting DC power cables.

8. Connect positive primary power wire (+13.8VDC) to terminal marked +13.8VDC and negative primary power wire to GND terminal on rear of amplifier.

9. Check your work before applying DC voltage to the system. Make certain all connections are tight and the DC wires are going to the correct terminals.

10. Refer to Section 3 for initial start-up procedures.

NOTE:

1. Make sure power supply DC is well filtered and well behaved with minimal voltage overshoot.

2. Keep DC wires as short as possible to minimize inductance induced voltage transients.

3. Size DC Wires properly to handle the load current to minimize voltage drop.

2.5. AMPLIFIER SUMMARY ALARM AND POWER CUTBACK CONTROL

The summary alarm and cutback control connections are made through separate filtered feedthrough connectors on the back of the amplifier.

Table 2-1. Summary Alarm and Cutback Control Connections

PIN FUNCTION DESCRIPTION CONDITION

APPROPRIATE

LOAD

ALARM

CTRL

SH/D

Summary Alarm

Partial Power Cutback

External Power Control

Indicates when:

1. The output power is low, or

2. VSWR cutback is activated, or

3. Thermal cutback is activated

Used as a simple means of cutting back output power by a fixed amount (1-1.5 dB).

It is possible to reduce the output power continuously by up to 4 dB by connecting a resistor between this pin and ground.

Normal Operation: < 1 VDC Alarm: > 8 VDC (up to Vcc)

Normal Operation: < 1 VDC Alarm: 4 - 5 VDC

Normal Operation – pin not connected.

Cutback Mode – pin pulled to ground. The output power reduces by approximately 1dB-1.5 dB.

Normal Operation – pin not connected.

Power Control Mode – pin pulled to ground through resistor.

> 10 kOhm, < 100pF

1.8 kOhm between pin and ground, <500 pF (TTL compatible)

<10 Ohm, < 100pF

Resistor value 0-50 kOhm, <100 pF

3. GENERAL OPERATING INFORMATION

3.1. INTRODUCTION

This section contains operating instructions for the amplifier.

3.2. STATUS INDICATORS

The function of the amplifier status indicators and is described in Table 3-1.

Table 3-1. Amplifier Status Indicators

STATUS LED FUNCTION

DC ON

LOW OUTPUT

HIGH VSWR

HIGH TEMP

3.3. INITIAL STARTUP

To perform the initial start-up, proceed as follows: Check to ensure that all input and output cables are properly connected and tightened. Note: Use high quality coaxial cable and connectors. Properly install and solder all

connectors for reliability.

CAUTION:

NOTE:

2. Apply DC power to the amplifier. Verify that the power supply measures 13.8 ± 0.1VDC. The fan will come on immediately for a few seconds and then turn off.

3. Visually check the indicators on each amplifier module, and verify the following:

a. The DC PWR ON indicator (green) should be on. b. All ALARM LED indicators (red) should be off.

4. Turn on external exciter/transceiver and apply RF input signal. The fan should turn on after approximately 3 seconds.

5. Turn off RF input signal. The fan should continue running, but turn off after approximately 6-12 seconds.

Green LED. Illumination indicates DC Power has been applied.

Red LED. Activates when the output power drops to approximately 70-85% of set output power.

Red LED. Activates when load VSWR exceeds approximately

2.5:1. Red LED. Activates when the amplifier exceeds a safe operating

temperature.

Before applying power, make sure that the input and output of the amplifier are properly terminated in 50 ohms. Do not operate the amplifier without a load attached. Refer to Table 1-2 for input power requirements. Excessive input power will damage the amplifier. The output coaxial cable between the amplifier and the antenna must be 50 ohm coaxial cable.

4. PRINCIPLES OF OPERATION

4.1. INTRODUCTION

This section contains principles of operation of the RF Power Amplifier.

4.2. RF INPUT SIGNAL

The amplifiers are set at the factory to work over different input power ranges. The available range of inputs ranges may be found in Table 1-2.

4.3. RF OUTPUT LOAD

The load impedance should be as good as possible (VSWR <1.2:1) in the working band for good power transfer to the load and maximum amplifier efficiency.

4.4. FUNCTIONAL DESCRIPTION

The amplifier is a single channel CW amplifier that operates over the VHF frequency range. The amplifier specifications are listed in Tables 1-1 and 1-2.

4.4.1. MAIN RF PATH

The typical main RF path consists of an input attenuator, driver, splitter, final stage(s), combiner, rf detectors and harmonic filter. The circuitry becomes active upon the sensing of rf input power. This occurs when rf input reaches approximately 3 dB below the low end of the input power range. This keeps standby current at a minimum (< 20 mA) when rf input is not present (or is below the turn on level).

4.4.2. LOOP CONTROL

The loop control circuitry includes circuitry to works to maintain a constant output power versus variations in DC voltage, rf input power, frequency and load. A coupled detector at the output monitors the final RF output level and generates a DC voltage proportional to the RF output level. This voltage is fed back to the controller. The circuitry compares this voltage to a reference voltage and varies the gain of the amplifier to maintain a constant output.

4.4.3. VSWR PROTECTION

Reflected power is detected at the output of the amplifier and compared to forward power. When reflected power reaches an equivalent VSWR of approximately 2.5:1, the amplifier output is reduced to protect the finals and the front panel HIGH VSWR LED activates. The higher the load VSWR, the more the output power is reduced.

4.4.4. THERMAL PROTECTION

The heat sink temperature is monitored with a thermostat. When the heat sink temperature reaches an unsafe level, the output power of the amplifier is reduced by approximately 50%. This keeps the channel on the air while still providing some short term protection until the customer can address the underlying cooling issue.

4.5. AMPLIFIER COOLING

The amplifier is cooled with forced air over a large heat sink. It is important to keep a minimum clearance of 3 inches behind the amplifier and allow the coolest air possible to circulate through the fan.

5. MAINTENANCE

5.1. INTRODUCTION

This section contains periodic maintenance and performance test information for the amplifier.

NOTE:

5.2. PERIODIC MAINTENANCE

Periodic maintenance requirements are listed in Table 5-1. Table 5-1 also lists the intervals at which the tasks should be performed.

WARNING:

TASK INTERVAL ACTION Clean Air Vents/Check Fan Inspect Cables and Connectors and General Site Conditions

5.3. CLEANING AIR INLETS/OUTLETS

The air inlets and outlets should be checked every 30 days and cleaned if necessary. If the equipment is operated in a severe dust environment, it should be checked and cleaned more often. If dust and dirt are allowed to accumulate, the cooling efficiency will be diminished. Using either compressed air or a brush with soft bristles, loosen and remove accumulated dust and dirt from the air inlet panels.

Check that the fan is running smoothly. A slow running or noisy fan may indicate an imminent fan failure. Replace immediately with a similar to insure long term reliability. Heat is one of the biggest factors in reducing the reliability of your amplifier. Make sure the fan has access to cool and clean airflow within the rack.

Check your sales order and equipment warranty before attempting to service or repair the unit. Do not break the seals on equipment under warranty or the warranty will be null and void. Do not return equipment for warranty or repair service until proper shipping instructions are received from the factory.

Wear proper eye protection to avoid eye injury when using

compressed air.

Table 5-1. Periodic Maintenance

30 Days Inspect and clean per paragraph 5-3.

Verify fan is working properly.

6 Months Inspect signal and power cables for

frayed insulation and proper attachment. Check RF connectors to make sure that they are tight. Inspect the lightning protection system and ground at the site.

5.4. TEST EQUIPMENT REQUIRED FOR TEST

Test equipment required to test the amplifier performance is listed in Table 5-2. Equivalent test equipment may be substituted for any item.

NOTE:

All RF test equipment must be calibrated to 0.05 dB resolution. Any deviation from the nominal attenuation must be accounted for and factored into all output readings.

Table 5-2. Test Equipment Required (or equivalent)

EQUIPMENT MANUFACTURER MODEL

Signal Generator (1) H.P. 8657B 30 dB Attenuator, 200 Watt (1) Tenuline 8322 DC power supply (1) H.P 6673A Spectrum Analyzer (1) H.P. 8560E Power Meter (1) HP E4418A Power Meter (1) HP E4419A Power Sensor (3) HP 8481A Pad (3) Mini-Circuits NAT-20 Coupler (2) Narda 3020A Coupler Load (1) Lab Amplifier (1) AR 30W1000M7

5.5. PERFORMANCE TEST

Performance testing may be conducted to ensure that the amplifier system meets the operational specifications listed in Tables 1-2 and 1-3. The test equipment required to perform the testing is listed in Table 5-2 and the test setup is shown in Figure 5-1.

Watt Meter

s e

20 dB

Power

Supply

20 dB

Lo ad

Signal

Generator

Lab

Amplifier

Coupler

UUT Coupler Attenuator

30 dB

Figure 5-1. Amplifier Test Setup Diagram

Spectrum Analyzer

6. TROUBLESHOOTING

6.1. INTRODUCTION

This section contains a list of potential problems and suggested actions to be taken. If the suggested corrective action does not eliminate the problem, please contact your Crescend factory for further instructions.

NOTE: Check your sales order and equipment warranty before attempting to service or repair the unit. Do not break the seals on equipment under warranty or the warranty will be null and void. Do not return equipment for warranty or repair service until proper shipping instructions are received from the factory.

6.2. TROUBLESHOOTING

Refer to Table 6-1 for troubleshooting suggestions. It has been found that in some cases it may be necessary to power cycle an amplifier (turn DC power off and back on without RF applied) to clear an alarm.

Table 6-1. Troubleshooting

INDICATOR LED STATUS OUTPUT POWER STATUS POSSIBLE CAUSE SUGGESTED ACTIONS

(Green) LOW

OUTPUT (Red)

HIGH VSWR (Red)

OVER TEMP (Red)

Unlit No power No voltage at unit 1. Check power supply voltage DC PWR ON On Set power Normal operation 1. No action required On (all other alarm LEDs off)

On (together with HIGH VSWR alarm LED)

On Less than set power Output load VSWR is

On Less than set power

Less than set power

Frequency is out of range

The input power is below the low end of the rated input range

Power supply voltage is too low

Problem inside amplifier

Output load VSWR is much above 2.5:1

above 2.5:1

Fan is not rotating 1. Check if +13 VDC is present

Power supply voltage is too low causing insufficient air flow

Operating temperature of amplifier is exceeding safe level. Note: When unit cools, LED turns off and output returns to rated power

1. Check frequency

1. Check input power

1. Check power supply voltage at amplifier DC connector during key-up

1. Send the unit back to factory

1. Turn off amplifier (or remove RF input)

2. Check output connections and cables for integrity and tightness

3. Check antenna, combiner, etc. for proper return loss

1. Turn off amplifier (or remove RF input)

2. Check output connections and cables for integrity and tightness

3. Check antenna, combiner, etc. for proper return loss

on the FAN feedthrough pin when rf input present (after 3 sec turn on delay)

2. Check if anything is physically stopping rotation

3. If fan has failed, replace fan with same or similar fan

1. Check power supply voltage

2. Make sure that air access to front and rear of unit is unimpeded

3. Verify that air vents are clear of dust and dirt and that fan(s) are operating properly. Replace fan if necessary

4. Check ambient temperature (not to exceed spec - see Table 1-2)

6.3. RETURN FOR SERVICE PROCEDURES

When returning products to Crescend, the following procedures will ensure optimum response.

6.3.1. OBTAINING AN RMA

A Return Material Authorization (RMA) number must be obtained prior to returning equipment to the factory for service. Please contact our Customer Service Department at 800-872-6233 to obtain this number. Failure to obtain this RMA number may result in considerable delays in receiving repair service.

6.3.2. REPACKAGING FOR SHIPMENT

To ensure safe shipment of the amplifier, it is recommended to use the packaging designed for the amplifier. The original packaging material is reusable. If it is not available, contact Crescend’s Customer Service Department for packing materials and information.

Crescend Technologies VHFP15XXFF1 Users Manual

Specifications and Main Features

Frequently Asked Questions

User Manual