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136-174 MHz, 110 WATT POWER AMPLIFIER
19D902797G1
TABLE OF CONTENTS
DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Front Cover
SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
CIRCUIT ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
POWER AMPLIFIER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Exciter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Low Level Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
PA Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Power Amplifier Finals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
POWER CONTROL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Signal Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
TROUBLESHOOTING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
IC DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
PRODUCTION CHANGES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
POWER AMPLIFIER ASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
LOW PASS FILTER MODULE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
OUTLINE DIAGRAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
POWER AMPLIFIER SCHEMATIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
DESCRIPTION
The VHF Power Amplifier Assembly is a wide band RF
power amplifier operating over the entire 136 to 174 MHz
range without tuning or band splitting. Its main function is
to amplify the 10 mW FM signal from the Transmitter
Synthesizer to the rated RF output of 110 watts at the antenna
port. The output of the Power Amplifier Assembly is adjust-
able from 65 to 135 watts at the PA output J104. This
corresponds to a rated RF output of 55 to 110 watts at the
antenna.
The assembly consists of a printed wiring board (A1)
and associated components, including a power module and
three RF power transistors, mounted to the heat sink assem-
bly. The printed wiring board (A1) contains both the power
Maintenance Manual
LBI-38531G
Page
amplifier circuitry (100 series components) and the power
control circuitry (200 series components).
Unfiltered supply voltage, A+, for the power amplifier
circuits enters the assembly via feedthrough capacitor, C1.
Power cable W4 routes the A+ from CI to J103 on the PWB.
Filtered A+ voltage for the power control circuit enters the
assembly via control cable W13 which connects to the PWB
at J201.
The Power Control circuitry sets the output power level
by adjusting the PA Power Set level. It keeps the output
power constant despite variations in input power, power
amplifier gain, or temperature through the use of a feedback
control loop in the PA assembly.
M/A-COM Wireless Systems
3315 Old Forest Road
Lynchburg, Virginia 24501
(Outside USA, 434-385-2400) Toll Free 800-528-7711
www.macom-wireless.com
Printed in U.S.A.
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Summary of Contents for M/A-Com 19D902797G1
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Page 1: Table Of Contents
PA assembly. three RF power transistors, mounted to the heat sink assem- bly. The printed wiring board (A1) contains both the power M/A-COM Wireless Systems 3315 Old Forest Road Lynchburg, Virginia 24501 (Outside USA, 434-385-2400) Toll Free 800-528-7711 www.macom-wireless.com... -
Page 2: Specifications
M/A-COM Private Radio Systems, Inc., at any time and without notice. Such changes will be incorporated into new editions of this manual. -
Page 3: Power Amplifier Finals
LBI-38531G drop to zero (0) volts and the PA alarm light on the station power (zero watts) corresponds to 2.5 volts while maximum Power Amplifier Finals (Q102, Q103) will turn on. power corresponds to 4.5 volts. This voltage is not temperature compensated and no effort is made to calibrate this signal to an Each of the Power Amplifier Final devices is capable of absolute power level. -
Page 4: Troubleshooting Guide
LBI-38531G VHF POWER AMPLIFIER VOLTAGE CHART TROUBLESHOOTING GUIDE PARAMETER REFERENCE READINGS SYMBOL (volts DC) (50 OHM, -30° TO +60° C) SYMPTOM AREAS TO CHECK INDICATIONS 13.4 V ±20% SUPPLY VOLTAGE 1. No Power or low Power at 1. Measure the transmitter output power The presence of power at this port is an Antenna Port before the duplexer or antenna switch... -
Page 5: Ic Data
IC DATA PARTS LIST LBI-38531G U100 19A705532P2 VOLTAGE REGULATOR U101 344A3221P1 MMIC AMPLIFIER U102 19A70532P1 PA AMPLIFIER MODULE... -
Page 6: Production Changes
R 2 2 4 f r o m 10 K oh m s ( 19 B 80 06 07 P 10 3) t o 22 K oh m s (19B800607P223). Added D211 (19A700025P6) between Q201-C (cathode) and Q201-E (anode). REV. A - POWER AMPLIFIER MODULE, 19D902797G1 REV. A - POWER AMPLIFIER BOARD 19D902794G1 To improve reliability. -
Page 7: Power Amplifier Assembly
ASSEMBLY DIAGRAM LBI-38531G (19B801659, Sh. 2, Rev. 3) POWER AMPLIFIER ASSEMBLY POWER AMPLIFIER ASSEMBLY 19D902797G1 19D902797G1 (19D902797, Sh. 2, Rev. 14) (19D902797, Sh. 1, Rev. 14) -
Page 8: Low Pass Filter Module
ASSEMBLY, OUTLINE & SCHEMATIC DIAGRAMS LBI-38531G LOW PASS FILTER MODULE LOW PASS FILTER MODULE 19D902856G1 19D902856G1 (19D902853, Sh.1, Rev. 2) (19D902854, Comp. Side, Rev. 9A) (19D902856 Sh. 1, Rev. 1) -
Page 9: Outline Diagrams
LBI-38531G OUTLINE DIAGRAM POWER AMPLIFIER BOARD A1 POWER AMPLIFIER BOARD A1 19D902794G1 REV. B AND EARLIER 19D902794G1 REV. C AND LATER (19D902794, Sh 1, Rev 15) (19D902794, Sh.1, Rev. 18) -
Page 10: Power Amplifier Schematic
SCHEMATIC DIAGRAM LBI-38531G POWER AMPLIFIER ASSEMBLY 19D902797G1 (19D902798, Sh. 1, Rev. 9) - Page 11 SCHEMATIC DIAGRAM LBI-38531G POWER AMPLIFIER ASSEMBLY 19D902797G1 REV. B AND EARLIER (19D902798, Rev. 4)
- Page 12 SCHEMATIC DIAGRAM LBI-38531G POWER AMPLIFIER ASSEMBLY 19D902797G1 REV. C AND LATER (19D902798, Rev. 9)
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