RF Technology PA 150 Manual de usuario
Eclipse Series
RF Technology
February, 2003
PA 150 Amplifier
Operation and Maintenance Manual
This manual is produced by RF Technology Pty Ltd
10/8 Leighton Place, Hornsby NSW 2077 Australia.
Copyright © 1997 RF Technology.
RF Technology PA150 Page 2
CONTENTS CONTENTS
Contents
1 Operating Instructions 3
1 1.1 Front Panel Indicators 3
1.2 Internal Adjustments 3
1.3 Output Power 3
1.4 RF Level Detector 3
2 Circuit Description 4
2.1 Amplifiers 4
2.2 Power Splitter/Combiners 5
2.3 Directional Coupler 5
2.4 Low pass Filter 5
2.5 Power Control Circuits 5
2.6 RF Output Indicator 5
2.7 Over Temperature Protection 6
3 Alignment Procedure 6
4 Specifications 7
4.1 Description 7
4.2 Physical Configuration 7
4.3 Front Indicators and Test Points 7
4.3.1 Indicators 7
4.3.2 Test Points 8
5 Electrical Specifications 8
5.1 Power Requirements 8
5.2 Frequency Range 8
5.3 Nominal Antenna Impedance 8
5.4 Output Power 8
5.5 Transmit Duty Cycle 8
5.6 Spurious and Harmonics 8
5.7 Maximum Heatsink Temperature 9
5.8 ALC Output 9
5.9 Mis-Match Protection 9
6 Conectors 9
6.1 Antenna Connector 9
6.2 Power and I/O Connector 9
6.3 Test Connector 9
7 Appendix A Block Diagram 10
Schematic Diagram
Board Layout 11
Parts List 12
RF Technology PA150 Page 3
1 OPERATING INSTRUCTIONS
1Operating Instructions
1.1 Front Panel Indicators
PWR LED
The Power LED shows that the dc supply is connected to the transmitter.
RFO LED
The RF Output LED indicates that the amplifier is being driven and that
the forward output power is above a preset level. The indication level is
set by RV1 which is accessible through the side of the case. (After
removing 20 screws)
TEMP LED
The Temperature LED indicates when the amplifier temperature
is too high. The power is automatically reduced if the output transistors
temperature rises above safe limits.
1.2 Internal Adjustments
All internal adjustments are factory set and should not need readjustment under
normal conditions.
1.3 Output Power
The output power is set to the desired level watts by RV2. It determines the
threshold of the ALC voltage which is fed back to the transmitter module to
regulate the power. The output power of standard amplifiers can be set to any
level between 25 and 75 watts. The high power versions with “H” suffix model
numbers can be set between 50 and 100 watts.
WARNING
Changes or modifications not expressly approved by
RF Technology could void your authority to operate
this equipment. Specifications may vary from those
given in this document in accordance with
requirements of local authorities. RF Technology
equipment is subject to continual improvement and RF
Technology reserve the right to change performance and
specification without further notice.
RF Technology PA150 Page 4
2 CIRCUIT DESCRIPTION
1.4 RF Level Detector
The RF Detector threshold for the RFO LED on the amplifier front panel is set by
RV1. This is normally set at half the rated output power.
PA150 Amplifier I/O Connections
25 Pin Connector
Function/Signal Pins Specification
DC Power +12Vdc
-0Vdc 1,2,14,15
12,13,24,25 +11.4 to 16Vdc
ALC Output 8 Approx 7Vdc decreasing with
increasing power or temperature
RF Input
BNC Connector 25 Watts max
RF Output
N Connector 120 Watts Max
2Circuit Description
The following descriptions should be read as an aid to understanding the block and
schematic diagrams at the rear of this manual.
2.1 Amplifiers
The RF power amplification is provided by one or two transistors, Q4 and Q5.
The standard power version uses one transistor (Q4) and the high power version
uses two. Each transistor is rated at 75 watts output. The input and output
impedances of the transistors are matched to 50O by microstrip matching
networks.
WARNING
Ensure that the output power setting complies with the equipment’s licence
requirements. Failure to do so may result in penalties being imposed by the
licensing authority.
RF Technology PA150 Page 5
2 CIRCUIT DESCRIPTION
The amplifiers are broad band and do not have any tuning adjustments. The “A”
versions are optimized for the frequency range 136-156 MHz while the “B”
versions cover 154-174 MHz.
The dc supply is fed to the amplifiers through resistors R21 and R22. This allows
the collector current of each amplifier to be measured at the test socket.
2.2 Power Splitter/Combiners
The high power versions use zero degree power splitters and combiners. They
consist of lumped element 1/4 wave 70O pi networks and 100O RF resistors (C43-
50, L17-20, R19-20). This configuration provides wider bandwidth and better
balance than lower cost 90 degree hybrids.
2.3 Directional Coupler
The forward and reverse power components are measured throug a coupled line
directional coupler. The output of the coupled line is frequency compensated by
R1-4 and C51-52 before being detected by D1 and D3.
The voltage output of the detectors is proportional to the forward and reflected
power.
2.4 Low Pass Filter
A low pass filter consisting of L12-16 and C39-42 reduces the harmonic
components to less than -80dBc. The filter uses a combination of lumped
elements and printed microstrips to obtain the required harmonic attenuation.
2.5 Power Control Circuits
The forward and reverse voltages from the directional coupler are amplified and
inverted by U2a and U2b. The amplified voltages are combined before
connecting to the input of error amplifier U2d.
Error amplifier U2d compares the detected voltage with the dc reference voltage
from output power trimpot RV2. The amplified difference at the output U2d is
supplied to the rear panel system connector for connection to the T150 ALC input.
2.6 RF Output Indicator
The forward power voltage is compared with the pre-set dc reference voltage from
RV1 and U2c. The output of U2c is used to turn on the RFO LED and provide an
output power logic signal to the test connector.
RF Technology PA150 Page 6
3 ALIGNMENT PROCEDURE
RV1 is normally set so that the RFO LED comes ON at 1-3 db below the normal
power output.
2.7 Over Temperature Protection
Thermistor RT1 is mounted to the case of output transistor Q4. If the transistor
case temperature rises above 90 degrees C the resistance of RT1 increases and Q2
is turned ON.
This causes the TEMP LED to come on and also reduces the dc reference voltage
to the output power error amplifier U2d. The input power will then be reduced by
the transmitter ALC circuits and the output transistors are kept within safe
operating limits.
3Alignment Procedure
The following procedures may be used to align the amplifier for optimum
performance.
Standard Test Conditions
RF Input Source Power Supply Load
T150 Series transmitter
25 watts maximum 13.8 Vdc at 15 A 50O 150 watts
VSWR < 1.2:1
Set RFO Level
Step Input Measure Adjust
1 None Set RV1 and R2 Fully counter
clockwise
2 Centre channel
frequency from the
T150, 25W max
threshold
RF output power at
J2 Key transmitter
adjust RV2 for
desired output
3 As above RFO LED Key transmitter
adjust RV1 to
where the RFO
LED just goes OFF
RF Technology PA150 Page 7
4 SPECIFICATIONS
Set Output Power
Step Input Measure Adjust
4 As above RF output power at
J2 Key transmitter.
Adjust RV2 for the
desired power
4Specifications
4.1 Description
The power amplifiers are designed for use with the T150 series transmitters to
provide 50-150 watts output.
Output power regulation is provided by connecting the output of the directional
coupler to the ALC input of the T150. the drive from the transmitter is then
automatically adjusted to maintain the required output.
The regulated power level can be preset over a wide range from 25 to 150 watts
depending on the available driver power.
Sensing circuits are provided to protect the output transistors from excessive
temperatures. If the output transistor case temperature rises to 90 degrees C, the
input drive will be reduced to prevent damage.
4.2 Physical Configuration
The power amplifier is designed to fit in a 19 inch rack mounted frame. The
installed height is 4RU (178mm) and the depth is 350mm. The amplifier is
95.25mm or three Elcipse modules wide.
An extruded aluminium heat sink with vertical fins is used. The temperature rise
is normally less than 30 degrees at 50 watts output.
4.3 Front Indicators and Test Points
4.3.1 Indicators
Power ON -Green LED
RF Power Output -Yellow LED
Over Temperature -Red LED
RF Technology PA150 Page 8
5 ELECTRICAL SPECIFICATIONS
4.3.2 Test Points (DB9 Connector)
Forward Power Pin 8 + Gnd (pin 1)
Reverse Power Pin 4 + Gnd (pin 1)
Collector Current Pin 6, Pin 2 + Vcc 13.2Vdc
5Electrical Specifications
5.1 Power Requirements
Operating Voltage -10.5 to 16 Vdc with output power reduced below 12.5 Vdc.
Current Drain @ 13.2 Vdc -10 Amps Max at 50 watts. 100 mA Max standby
Polarity -Negative Ground
5.2 Frequency Range
Frequency 50 Watt 100 Watt
136-156MHz PA150A PA150AH
154-174 MHz PA150B PA150BH
5.3 Nominal Antenna Impedance
50O
5.4 Output Power
25 to 100 watts adjustable
5.5 Transmit Duty Cycle
With Free Air Circulation
50 Watts -100% to 40 deg. C
100 Watts -50% to 40 deg. C
With Fan Module
50-100 Watts -100% to 50 deg. C
5.6 Spurious and Harmonics
Less than 0.25uW
RF Technology PA150 Page 9
Connectors
5.7 Maximum Heatsink Temperature
90 degrees C.
5.8 ALC Output
The ALC is intended for connection to the T150. It supplies a voltage which
decreases with increasing power or temperature.
5.9 Mis-Match Protection
The amplifier is protected from damage when operating into a VSWR of 10/1 at
all phase angles.
6Connectors
6.1 Antenna Connector
Type N Female mounted on the module rear panel
6.2 Power and I/O Connector
25 pin “D” Male mounted on the rear panel
6.3 Test Connector
9 pin “D” Female mounted on the front panel.
RF Technology PA150 Page 10
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