Crescend Technologies VHFP15XXFF1 AMPLIFIER User Manual USERS MANUAL

Crescend Technologies LLC AMPLIFIER USERS MANUAL

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USERS MANUAL

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

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: INDICATORS

DC ON (Green), LOW OUTPUT (Red),

HIGH VSWR (Red), OVER TEMP (Red)

Alarm and Control Pins:

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

Frequency

Range (MHz) Input Power

Range (W) Rated Output

Power (W)

Typ

Current

(A)

Max

Current

(A)

Spurious

and

Harmonic

s (dBc)

136-144 (DA)

144-152 (DB)

152-162 (EA)

162-174 (EB)

0.1-0.2

0.2-0.5

0.5-1

1-2

2-5

5-10

10-20

20-50

80 (P8)

100 (P10)

110 (P11)

150 (P15)

<-65

<-67

NOTES: Manufacturer’s Rated Output Power of this Equipment is for

Single Carrier Operation.

All specifications above apply at +13.8 ± 0.1 VDC operating

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

2. INSTALLATION

2.1. INTRODUCTION

This section contains installation recommendations, unpacking, inspection, and installation

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: Exercise care in handling equipment during inspection to

prevent damage caused by rough or careless handling.

Visually inspect the amplifier module for damage that may have occurred during shipment.

Check for evidence of water damage, bent or warped chassis, loose screws or nuts, or

extraneous packing material in the connector or fans. Inspect the rear panel connector for

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 to the rear of the rack

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

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

Normal Operation: < 1 VDC

Alarm: > 8 VDC (up to Vcc) > 10 kOhm,

< 100pF

ALARM Summary

Alarm

Indicates when:

1. The output power is low,

2. VSWR cutback is

activated, or

3. Thermal cutback is

activated

Normal Operation: < 1 VDC

Alarm: 4 - 5 VDC

1.8 kOhm

between pin and

ground,

<500 pF

(TTL

compatible)

Normal Operation – pin not

connected.

CTRL Partial

Power

Cutback

Used as a simple means of

cutting back output power

by a fixed amount (1-1.5

dB).

Cutback Mode – pin pulled

to ground. The output

power reduces by

approximately 1dB-1.5 dB.

<10 Ohm,

< 100pF

Normal Operation – pin not

connected.

SH/D External

Power

Control

It is possible to reduce the

output power continuously

by up to 4 dB by connecting

a resistor between this pin

and ground. Power Control Mode – pin

pulled to ground through

resistor.

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

Green LED. Illumination indicates DC Power has been applied.

LOW OUTPUT

Red LED. Activates when the output power drops to approximately

70-85% of set output power.

HIGH VSWR

Red LED. Activates when load VSWR exceeds approximately

2.5:1.

HIGH TEMP

Red LED. Activates when the amplifier exceeds a safe operating

temperature.

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: 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.

NOTE:

The output coaxial cable between the amplifier and the antenna

must be 50 ohm coaxial cable.

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.

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:

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.

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: Wear proper eye protection to avoid eye injury when using

compressed air.

Table 5-1. Periodic Maintenance

TASK INTERVAL ACTION

Clean Air Vents/Check

Fan 30 Days Inspect and clean per paragraph 5-3.

Verify fan is working properly.

Inspect Cables and

Connectors and General

Site Conditions

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.

5.3. 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.

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.

Figure 5-1. Amplifier Test Setup Diagram

Signal

Generator Lab

Amplifier Coupler

UUT Coupler Attenuator

30 dB Spectrum

Analyzer

Power

Supply

dB 20

Watt Meter

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

Unlit No power No voltage at unit 1. Check power supply voltage DC PWR ON

(Green) On Set power Normal operation 1. No action required

Frequency is out of

range 1. Check frequency

The input power is

below the low end of

the rated input range

1. Check input power

Power supply voltage

is too low 1. Check power supply voltage

at amplifier DC connector

during key-up

On (all other

alarm LEDs

off)

Problem inside

amplifier 1. Send the unit back to factory

LOW

OUTPUT

(Red)

On (together

with HIGH

VSWR alarm

LED)

Less than set power

Output load VSWR is

much above 2.5:1 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

HIGH VSWR

(Red) On Less than set power Output load VSWR is

above 2.5:1 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

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

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

Power supply voltage

is too low causing

insufficient air flow

1. Check power supply voltage

OVER TEMP

(Red) On Less than set power

Operating

temperature of

amplifier is exceeding

safe level. Note:

When unit cools, LED

turns off and output

returns to rated power

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 AMPLIFIER User Manual USERS MANUAL

Crescend Technologies LLC AMPLIFIER USERS MANUAL

USERS MANUAL

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