Eclipse Series
RF Technology
rfinfo@rftechnology.com.au
January, 2004
PA70 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
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RF Technology PA70 Page 2
CONTENTS CONTENTS
Contents
1 Operating Instructions 3
1.1 Front Panel Indicators 3
1.2 Internal Adjustments 3
2 Circuit Description 4
2.1 Amplifier 4
2.2 Directional Coupler 5
2.3 Low Pass Filter 5
2.4 Power Control Circuits 5
2.5 RF Output Indicator 5
2.6 Over Temperature Protection 5
3 Alignment Procedure 6
3.1 Standard Test Conditions 6
4 Specifications 8
4.1 Description 8
4.2 Physical Configuration 8
5 Front Indicators and Test Points 9
5.1 Indicators 9
5.2 Test Points 9
6 Electrical Specifications 9
6.1 Power Requirements 9
6.2 Frequency Range 9
6.3 Nominal Antenna Impedance 9
6.4 Output Power 9
6.5 Transmit Duty cycle 9
6.6 Spurious and Harmonics 10
6.7 Maximum Heatsink Temperature 10
6.8 ALC Output 10
6.9 Mis-Match Protection 10
7 Connectors 10
7.1 Antenna Connector 10
7.2 Power and I/O Connector 10
7.3 Test Connector 10
8 Parts List 11
Schematic Diagram
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RF Technology PA70 Page 3
1 OPERATING INSTRUCTIONS
1 Operating 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 present 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 re-adjustment
unless the operating frequency is changed.
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
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
reserves the right to change performance and specifications
without further notice.
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RF Technology PA70 Page 4
2 CIRCUIT DESCRIPTION
regulate the power. The output power can be set to any level between 25 and
70 watts.
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.
Warning
Ensure that the output power setting complies with the equipment’s license
requirements. Failure to do so may result in penalties being imposed by the
licensing authority.
PA70 Amplifier I/O Connections
25 Pin Connector
Function Signal Pins Specification
DC Power +12 Vdc
0 Vdc
1,2,14,15
12,13,24,25
+11.4 to 16 Vdc
ALC Output 8 Approx 7 Vdc decreasing with
increasing power or temperature
RF Input
BNC Connector
25 Watts Max.
RF Output
N Connector
70 Watts Max.
2. Circuit 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 Amplifier
The RF power amplification is provided by a single transistor, Q4. The
transistor provides at least 10dB gain in the 66-88 MHz frequency range.
The input and output impedance of the transistor is matched to 50 O by
networks which use printed micro-strips and lumped elements. Variable
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RF Technology PA70 Page 5
2 CIRCUIT DESCRIPTION
capacitors C9, C12, C21 and C22 are used to tune the amplifier for optimum
performance on the operating frequency.
Although not a true broad band design, the amplifier provides good gain and
efficiency with frequency spreads of up to 5 MHz.
The dc supply is fed to the amplifier through resistor R21. This allows the
collector current to be measured at the test socket.
2.2 Directional Coupler
The forward and reverse power components are measured through 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 output voltage of the detectors is proportional to the forward and reflected
power.
2.3 Low Pass Filter
A low pass filter consisting of L8-12 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.
2.4 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 of U2d is supplied to the rear panel system connector for connection to
the T70 ALC input.
2.5 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.
RV1 is normally set so that the RFO LED comes ON at 1-3 db below the
normal power output.
2.6 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.
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RF Technology PA70 Page 6
3 ALIGNMENT PROCEDURE
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.
3 Alignment Procedure
The following procedure may be used to align the amplifier for optimum
performance.
3.1 Standard Test Conditions
RF Input Source
T70 series transmitter set for 10 Watts maximum output.
The ALC output from the PA70 must be connected to the T70 ALC input.
Power Supply
13.8 Vdc at 15A with a load current meter or a test meter connected to measure
the voltage between pins 2 and 5 of the PA70 test connector (0.1 Vdc = 1A)
RF Power Meter and Load
50O 0-70 Watts
VSWR <1.2:1
Directional RF Power Meter
50O 0-10 Watts
Forward and Reverse
OR
A dc test meter connected to measure the forward and reverse voltage at the
T70 test connector.
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RF Technology PA70 Page 7
3 ALIGNMENT PROCEDURE
Alignment
Step Input Measure Adjust
1 None
Set RV2 fully
clockwise
2 None
SetC11,C12,C20,
C21 to the middle
of their adjustment
range
3 Set T70 to the
centre frequency
channel
Reflected power at
the PA70 input/
T70 output
Key the transmitter
and adjust C9 and
C12 for minimum
reflected power.
4 As above Output power from
the PA70
Key the transmitter
and adjust C21 and
C22 for maximum
output power.
5 As above Refl. Pwr. = 0
Output > 70W
Repeat 3 and 4
until no further
improvement is
obtained.
6 As above Output power from
the PA70
Key the transmitter
and adjust RV2 to
set the power to
approximately 10%
above the desired
level.
7 As above dc current or
voltage at test pins
5-2 and output
power
Key the transmitter
and adjust C21 in
the direction of
decreasing dc
curent to the point
where the output
power just starts to
drop
8 As above Output power Key the transmitter
and set RV2 to
obtain the desired
output power
9 As above reflected power at
the PA70 input/T70
output
Key the transmitter
and adjust C9 and
C21 for minimum
reflected power
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RF Technology PA70 Page 8
4 SPECIFICATIONS
Set RFO Level
Step Input Measure Adjust
10 None
Set RV1 and R2
fully counter
clockwise
11 Centre channel
frequency from
T70, 10W max
RF output power at
J2
Key transmitter and
ajust RV2 for the
desired threshold
output power
12 As above RFO LED Key transmitter and
adjust RV1 to
where the RFO
LED just goes
OFF.
13 As above RF output power at
J2
Key transmitter and
adjust RV2 for the
desired power
4 Specifications
4.1 Description
The power amplifier is designed for use with the T70 series transmitters to
provide 25-70 watts output.
Output power regulation is provided by connecting the output of the directional
coupler to the ALC input of the T70. The drive from the transmitter module is
then automatically adjusted to maintain the required output.
The regulated power level can be preset over a wide range from 25 to 70 watts
depending on the available driver power.
Sensing circuits are provided to protect the output transistor 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 Eclipse 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.
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6 ELECTRICAL SPECIFICATIONS
5 Front Indicators and Test Points
5.1 Indicators
Power ON - Green LED
RF Power Output - Yellow LED
Over Temperature - Red LED
5.2 Test Points
Forward Power – Pin 8 + Gnd (pin 1)
Reverse Power - Pin 4 + Gnd (pin 1)
Collector Current – Pin 2 + 13.2Vdc (pin 5)
6 Electrical Specifications
6.1 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 70 Watts. 100 mA Max. standby
Polarity - Negative Ground
6.2 Frequency Range
Adjustable to cover 66 to 88 MHz with a maximum channel frequency spread
of 5 MHz.
6.3 Nominal Antenna Impedance
50O
6.4 Output Power
25 to 70 watts adjustable
6.5 Transmit Duty Cycle
With Free Air Circulation
50 Watts - 100% to 40 deg. C
70 Watts - 50% to 40 deg. C
With Fan Module
25-70 Watts - 100% to 50 deg. C
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RF Technology PA70 Page 10
7 CONNECTORS
6.6 Spurious and Harmonics
Less than 0.25µW
6.7 Maximum Heatsink Temperature
90 degrees C.
6.8 ALC Output
The ALC is intended for connection to the T70. It supplies a voltage which
decreases with increasing power or temperature.
6.9 Mis-Match Protection
The amplifier is protected from damage when operating into a VSWR of 5/1 at
all phase angles.
7 Connectors
7.1 Antenna Connector
Type N Female mounted on the module rear panel
7.2 Power and I/O Connector
25 Pin “D” Male mounted on the rear panel
7.3 Test Connector
9 Pin “D” Female mounted on the front panel.
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RF Technology PA70 Page 11
B
PA70 PARTS LIST
Ref. Description Part Number
C1 CAP 10N 10% 50V X7R RAD .2 46/2001/010N
C2 CAP 4N7 5% 400V MKT RAD.2 47/2040/04N7
C3 CAP 10U 35V RAD ELECTRO 41/2001/010U
C4 CAP 10N 10% 50V X7R RAD.2 46/2001/010N
C5 CAP 1NO 5% 63V NPO SM1206 46/3300/01N0
C6 CAP 1NO 5% 63V NPO SM1206 46/3300/01N0
C7 CAP 100N 10% 50V X7R RD.2 46/2001/100N
C8 CAP 10N 10% 50V X7R RAD.2 46/2001/010N
C9 CAP TRIM 7-100P HI TEMP 49/3003/100P
C11 CAP 27P 500V MICA SM1210 48/3003/027P
C12 CAP TRIM 7-100 HI TEMP 49/3003/100P
C13 CAP 1N0 500V MICA SM2220 48/3003/01N0
C14 CAP 6.8U 20% 25V SOLID AL 41/2225/06U8
C15 CAP 100N 10% 50V X7R RD.2 46/2001/100N
C16 CAP 100N 10% 63V X7R 1206 46/3310/100N
C17 CAP 1N0 500V MICA SM2220 48/3003/01N0
C18 CAP 1N0 5% 63V NPO SM1206 46/3300/01N0
C19 CAP 510P 500V MICA SM2200 48/3003/510P
C20 CAP 27P 500V MICA SM1210 48/3003/027P
C21 CAP TRIM 7-100P HI TEMP 49/3003/100P
C22 CAP TRIM 7-100P HI TEMP 49/3003/100P
C39 CAP 68P 500V MICA SM1210 48/3003/068P
C40 CAP 68P 500V MICA SM1210 48/3003/068P
C41 CAP 20P 500V MICA SM1210 48/3003/020P
C42 CAP 20P 500V MICA SM1210 48/3003/020P
C51 CAP 27P 5% NPO SM1206 46/3300/027P
C52 CAP 27P 5% NPO SM1206 46/3300/027P
C53 CAP 1NO 5% 63V NPO SM1206 46/3300/01N0
C54 CAP 1NO 5% 63V NPO SM1206 46/3300/01N0
C55 CAP 1NO 5% 100V NPO RAD.2 46/2000/01N0
C56 CAP 1NO 5% 100V NPO RAD.2 46/2000/01N0
C57 CAP 1NO 5% 100V NPO RAD.2 46/2000/01N0
C58 CAP 1N0 5% 100V NPO RAD.2 46/2000/01N0
C59 CAP 1NO 5% 100V NPO RAD.2 46/2000/01N0
C60 CAP 1NO 5% 100V NPO RAD.2 46/2000/01N0
C61 CAP 1NO 5% 100V NPO RAD.2 46/2000/01N0
D1 DIO SHTKY BAT17 SOT23 21/3030/0017
D2 DIODE SILICON IN4148 21/1010/4148
D3 DIO SHTKY BAT17 SOT23 21/3030/0017
L1 IND 1U 10% CHOKE SM1206 37/3320/01U0
L2 COIL AIR CORE 2T 2P 6.35D 37/1635/2002
L3 INDUCTOR 1uH AXIAL 37/2021/001U
L4 IND MOLDED 6.5 TURN 37/2021/0006
L5 COIL AIR CORE 7T 1.5P 6.35ID 37/1635/1507
L6 FERRITE BEAD 3x4x1 4S2 37/1022/0001
L7 COIL AIR CORE 2T 2P 6.35ID 37/1635/2002
L8 COIL AIR CORE 3T 1.5P 6.35ID 37/1635/1503
L9 COIL AIR CORE 5T 1.5P 6.35ID 37/1635/2005
L11 COIL AIR CORE 5T 2P 6.35ID 37/1635/2005
L12 COIL AIR CORE 3T 1.5P 6.35ID 37/1635/1503
P1 6.35mm QC TAB VERT PCB MT 35/0635/0001
P3 6.35mm QCTAB VERT PCB MT 35/0635/0001
P4 CON 16WAY SHR’D HEADER 35/2502/0016
Q1 TRSTR GP PNP 2N3906 TO92 27/2010/3906
Q2 TRSTR GP NPN 2N3904 TO92 27/2020/3904
Q3 TRSTR GP NPN 2N3904 TO92 27/2020/3904
Q4 TRSTR NPN VHF RF MRF492 27/3020/MRF492
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RF Technology PA70 Page 12
PA70 PARTS LIST
R1 RES 220 5% 0.25W SM1206 51/3380/0220R
R2 RES 220 5% 0.25W SM1206 51/3380/0220R
R3 RES 220 5% 0.25W SM1206 51/3380/0220R
R4 RES 220 5% 0.25W SM1206 51/3380/0220R
R5 RES 47K 5% 0.25W AXIAL 51/1040/047K
R6 RES 100K 5% 0.25W AXIAL 51/1040/100K
R7 RES 1K0 5% 0.25W AXIAL 51/1040/01K0
R8 RES 47K 5% 0.25W AXIAL 51/1040/047K
R9 RES 100K 5% 0.25W AXIAL 51/1040/100K
R10 RES 1K0 5% 0.25W AXIAL 51/1040/01K0
R11 RES 100 5% 0.25W AXIAL 51/1040/0100R
R12 RES 1M0 5% 0.25W AXIAL 51/1040/01M0
R13 RES 100K 5% 0.25W AXIAL 51/1040/100K
R14 RES 10K 5% 0.25W AXIAL 51/1040/010K
R15 RES 10K 5% 0.25W AXIAL 51/1040/010K
R16 RES 2K2 5% 0.25W AXIAL 51/1040/02K2
R17 RES 10K 5% 0.25W AXIAL 51/1040/010K
R18 RES 10K 5% 0.25W AXIAL 51/1040/101K
R19 RES 10R 5% 0.25W AXIAL 51/1010/0010
R21 RES 0.1R 5% 10W ASW 10 51/0010/00R1
R23 RES 10K 5% 0.25W AXIAL 51/1040/010K
R24 RES 270R 5% 0.25W AXIAL 51/1040/0270
R25 RES 270R 5% 0.25W AXIAL 51/1040/0270
R26 RES 680R 5% 0.25W AXIAL 51/1040/0680
R27 RES 10K 5% 0.25W AXIAL 51/1040/010K
R28 RES 10K 5% 0.25W AXIAL 51/1040/010K
R29 RES 10K 5% 0.25W AXIAL 51/1040/010K
R30 RES 47K 5% 0.25W AXIAL 51/1040/047K
R31 RES 33K 5% 0.25W AXIAL 51/1040/033K
R32 RES 33K 5% 0.25W AXIAL 51/1040/033K
R34 RES 47R 5% 2W AXIAL 51/1052/0047
R35 RES 47R 5% 2W AXIAL 51/1052/0047
R36 RES 4R7 5% 2W AXIAL 51/1052/04R7
R37 RES 2R2 5% 0.25W AXIAL 51/1040/02R2
R38 RES 47R 5% 2W AXIAL 51/1052/0047
R50 (P2) RES 100 5% 0.25W AXIAL 51/1040/0100
RT1 THERMISTOR 54/0400/0080
RV1 TRIMPOT 10K 1 TURN VERT 53/1020/010K
RV2 TRIMPOT 10K 1 TURN VERT 53/1020/010K
U1 IC VOLT REG 78LO8 TO92M 25/2040/78LO8
U2 IC QUAD OP AMP TLC274 25/2050/274C
PA70 LED Board Parts
D1 DIODE LED GREEN T1 3/4 21/1010/LEDG
D2 DIODE LED YELLOW T1 3/4 21/1010/LEDY
D3 DIODE LED RED T1 3/4 21/1010/LEDR
1 2 3 4
A
B
C
D
4321
D
C
B
A
T itle
Number RevisionSize
OrcadA
Date: 3-Aug-1998 Sheet of
File: D:\RF T _MasterFiles\..\9122-block.sch DrawnB y:
A MPL IFIE R PCB ASSY 11/9122
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13251224112310229218207196185174163152141
P5
CONNECT OR DB25
J3
J1
P1J2P2
P3
123456789
10111213141516
P4
123456789101112131415
16
J5
594837261
J6
CONNECT OR DB9
D1 D2 D3
+
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BNC
J2
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