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DESCRIPTION

The principle function of the Transmitter Synthesizer Mod-
ule is to provide the RF excitation for input to the MASTR®
III station power amplifier. The output of the synthesizer is
a frequency modulated signal at the desired frequency. The
module contains the following functional blocks:

A voltage controlled oscillator,

Frequency Doubler (Multiplier),

A chain of integrated circuit RF Amplifiers,

A reference buffer amplifier,

Dual modulus prescaler and synthesizer integrated
circuits,

Loop amplifiers and passive loop filter,

An audio amplifier and a pre-modulation integra-
tor.

IC voltage regulators for +5 and -5 Vdc, a discrete
component regulator for +8 Vdc, and an Opera-
tional Amplifier regulator for +4 Vdc.

Logic circuitry: address decoder, input signal gates,
and a lock indicator circuit.

CIRCUIT ANALYSIS

VOLTAGE CONTROLLED OSCILLATOR

Transistor Q1 and associated circuitry form a low noise
Voltage Controlled Oscillator (VCO). Inductor L1 and asso-
ciated capacitors form the oscillator resonant circuit (tank).
The noise characteristic of this oscillator is dependent on the
Q of this resonant circuit. The components used in the tank
are specified to have especially high Q. Diode D1 aids in
setting the bias point for low noise operation. (Any field
replacement of oscillator parts should use identical parts.)

Variable Capacitor C10 sets the fixed capacitance in the
tank, and therefore sets the frequency range over which the
oscillator can be voltage tuned.

The oscillator frequency is voltage tuned by the signal ap-
plied through R5 and L5 to the two varicap diodes D2 and
D3.  Additionally, audio modulation is applied as an AF
voltage to the two varicap diodes. This AF voltage varies the
oscillator frequency at an audio rate (i.e., it frequency modu-
lates the oscillator). Low frequency audio is applied along
with the varicap control voltage through R5 and L5 while
high frequency audio (MOD) is applied via C16.

Resistors R6 through R9 provide a two volt negative bias on
the varicap diodes.

Transistors Q101 and Q102 and associated circuitry form the
oscillator enable switch. This switch allows the station con-
trol circuitry to turn the VCO ON or OFF via the ANT_REL
line. Setting the ANT_REL line to a logic low causes Q102
to conduct. The five (5) volt output at Q102 collector
(OSCON) enables the fault indicator gates, U705-3 and
U705-4, and turns on Q101. Q101 starts to conduct, provid-
ing a ground path for Q1. This turns ON the VCO.

FREQUENCY DOUBLER

Transistors Q801 and Q802 form a buffer stage to drive
transistor multiplier Q803. The buffer isolates VCO Q1 from
loading effects which could degrade oscillator loaded Q and
hence noise performance. Transistor multiplier Q803 is
tuned to pass the second harmonic of the VCO output and
serves as a frequency doubler. Tank elements L802, C812-
C814 and L803 form a resonant circuit and matching net-
work to drive resistive splitter R201-R204.

RF AMPLIFIERS

The RF chain begins with resistive splitter R201-R204 and
R216-R218. The output of the splitter at R203 is attenuated
by 10 dB and provides impedance matching helical filter
FL201, which is tuned to pass the fundamental while reject-
ing harmonics by approximately 40 dB. The output of FL201
is fed thru resistive pad R205-R207 to MMIC Amplifier
U201 which operates in compression. U201 drives output
amplifier U202 into compression. The output amplifier is
followed by a bandpass filter (C208-C210, L203-L205) and
resistive attenuators (R210-R215). The final output at the
front panel BNC (J2) is nominally 11.5 dBm, and drives the
station Power Amp.

The other output of the resistive splitter at R218 is attenuated
by 20 dB and drives buffer amp U203 into compression.
U203 drives the synthesizer prescaler providing a feedback
signal for the synthesizer phase locked loop.

REFERENCE BUFFER AMPLIFIER

Transistor Q401 and associated components from a buffer
amplifier for the reference oscillator signal. (The reference
oscillator signal is produced by the receiver synthesizer
module of a MASTR III station.) The 0 dBm reference
oscillator signal is fed through the front panel BNC J1.
Resistor R405 provides a 50 ohm load to the reference
oscillator. The output of the Reference Buffer Amplifier is
fed directly to the synthesizer integrated circuit. The output
level at TP9 is approximately 3 volts peak to peak.

Copyright © 1992-2004, M/A-COM, Inc. All rights reserved.

TABLE 1:  GENERAL SPECIFICATIONS

ITEM

SPECIFICATION

FREQUENCY RANGE

450-470 MHz (G3)
425-450 MHz (G7)
403-430 MHz (G6)
380-400 MHz (G8)
470-494 MHz (G9)
490-512 MHz (G10)

CHANNEL SPACING

6.25 kHz

RF POWER OUT (50 Ohm load)

10 to 13 dBm
(10 to 20 mW)

RF HARMONICS

< -30 dBc

NON-HARMONIC SPURS

1 to 200 MHz

< - 90 dBc

200 MHz to 1 GHz

< - 60 dBc

CARRIER ATTACK TIME

<25 mSec

REFERENCE INPUT

input level

0 dBm 

±

1.5dB

input impedance

50 Ohm

frequency

5 to 17.925 MHz (must be integer divisible by 
channel spacing)

MODULATION SENSITIVITY

5 kHz peak dev/1 Vrms, Adjustable

AF INPUT IMPEDANCE

600 Ohm

AF RESPONSE

10 Hz

±

1.5 dB

1000 Hz0 dB reference
3 kHz

±

1.5 dB

10 Hz SQUARE WAVE MODULATION

<10%

Sq wave droop

HUM & NOISE

 -55 dB

POWER REQUIREMENTS

13.8 Vdc @ 275 mA
-12.0 Vdc @ 10 mA

This manual is published by 

M/A-COM, Inc.

, without any warranty. Improvements and changes to this manual necessitated by typographical errors, inaccuracies of current information, or improvements to programs

and/or equipment, may be made by 

M/A-COM, Inc.

, at any time and without notice. Such changes will be incorporated into new editions of this manual. No part of this manual may be reproduced or transmitted in

any form or by any means, electronic or mechanical, including photocopying and recording, for any purpose, without the express written permission of 

M/A-COM, Inc.

CREDITS

MASTR and EDACS are registered trademarks of M/A-COM, Inc.

All other brand and product names are trademarks, registered trademarks, or service marks of their respective holders.

LBI-38671N

1

Summary of Contents for MACOM 19D902780G3

Page 1: ...On page 6 of the manual update the production changes to include the following information Rev 4A Transmitter Synthesizer Board 19D902780G1 G3 G6 G8 Rev 9A Transmitter Synthesizer Board 19D902779G1 R...

Page 2: ...M A COM Wireless Systems 221 Jefferson Ridge Parkway Lynchburg Virginia 24501 Outside USA 434 385 2400 Toll Free 800 528 7711 www macom wireless com Printed in U S A...

Page 3: ...age 7 of the manual update the production changes to include the following information Rev 9A Transmitter Synthesizer Board 19D902779G3 Rev 7A Transmitter Synthesizer Board 19D902779G6 G8 Rev 4A Trans...

Page 4: ...Lynchburg Virginia 24501 Outside USA 434 385 2400 Toll Free 800 528 7711 www macom wireless com Printed in U S A M A COM Wireless Systems 221 Jefferson Ridge Parkway...

Page 5: ...IO FREQUENCY AMPLIFIER 2 VOLTAGE REGULATORS 2 LOGIC CIRCUITS 3 BLOCK DIAGRAM 2 MAINTENANCE 3 TEST PROCEDURE 3 ALIGNMENT PROCEDURE 3 TROUBLESHOOTING 3 PARTS LIST 4 PRODUCTION CHANGES 6 IC DATA 7 OUTLIN...

Page 6: ...cuit and matching net work to drive resistive splitter R201 R204 RF AMPLIFIERS The RF chain begins with resistive splitter R201 R204 and R216 R218 The output of the splitter at R203 is attenuated by 1...

Page 7: ...m of the audio modulation and the buffered error signal The output of the second buffer U501B is applied to a loop filter consisting of R506 R507 R508 C505 and C506 This filter controls the bandwidth...

Page 8: ...b Program synthesizer at 385 G8 455 G3 408 5 G6 430 G7 476 G9 or 497 G10 MHz Verify LED is off c Program synthesizer at 395 G8 465 G3 419 5 G6 445 G7 488 G9 or 507 G10 MHz Verify LED is off d Program...

Page 9: ...VDCW C13 19A702061P99 Ceramic 1000 pF or 5 50 VDCW temp coef 0 and or 30 PPM C C14 C15 19A700004P6 Metallized polyester 4 7 uF or 10 63 VDCW C16 19A702052P106 Ceramic 1500 pF or 5 50 VDCW C17 19A7020...

Page 10: ...4 7K ohms or 5 1 8 w R105 19B800607P392 Metal film 3 9K ohms or 5 1 8 w R201 19B800607P180 Metal film 18 ohms or 5 1 8 w and R202 SYMBOL PART NO DESCRIPTION R203 19B800607P150 Metal film 15 ohms or 5...

Page 11: ...o the required voltage level 2 5 0 05 V Changed capacitor C4 19A702236P8 of Schematic Diagram Sheet 1 Table of Values under column G3 From 1 5pF to 2 2 pF 19A702236P10 REV F TRANSMITTER SYNTHESIZER BO...

Page 12: ...5V Regulator U302 U601 19A116297P7 Dual Wide Band Op Amp U202 344A3907P1 Silicon Bipolar MMIC U303 19A704971P7 5V regulator U501 344A3070P1 Operational Amplifier U201 and U203 19A705927P11 Silicon Bi...

Page 13: ...l Modulus Prescaler 1 20 3 2 4 5 6 7 8 10 11 12 13 14 15 16 17 18 19 9 U402 19B800902P7 Synthesizer U502 19A702705P4 Quad Analog Switch U701 U705 19A703483P302 Quad 2 Input NAND Gate U702 19A703471P12...

Page 14: ...OUTLINE DIAGRAM UHF TRANSMITTER SYNTHESIZER BOARD 19D902779G3 G6 G10 19D902779 Sh 2 Rev 15 COMPONENT SIDE SOLDER SIDE LBI 38671N 9...

Page 15: ...SCHEMATIC DIAGRAM UHF TRANSMITTER SYNTHESIZER 19D902780G3 G6 G10 19D903363 Sh 1 Rev 22 LBI 38671N 10...

Page 16: ...SCHEMATIC DIAGRAM UHF TRANSMITTER SYNTHESIZER 19D902780G3 G6 G10 19D903363 Sh 2 Rev 22 LBI 38671N 11...

Page 17: ...SCHEMATIC DIAGRAM UHF TRANSMITTER SYNTHESIZER 19D902780G3 G6 G10 19D903363 Sh 3 Rev 22 LBI 38671N 12...

Page 18: ...SCHEMATIC DIAGRAM UHF TRANSMITTER SYNTHESIZER 19D902780G3 G6 G10 19D903363 Sh 4 Rev 22 LBI 38671N 13...

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