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Description; Circuit Analysis; Exciter; Icoms - GE MASTR II Maintenance Manual

20-50 mhz, 50-watt transmitter

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Maintenance manual (29 pages)

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DESCRIPTION

MASTR II transmitters are crystal-

controlled, phase modulated and designed

for one- through eight-frequency operation

in the 25 to 50 megahertz band.

The solid

state transmitter utilizes both integrated

circuits (ICs) and discrete components, and

consists of the following assemblies:

•

Exciter Board; with audio, modulator,

amplifier and multiplier stages.

•

Power Amplifier Assembly; with ampli-

fier, driver, PA, power control, fil-

ter and antenna switch.

CIRCUIT ANALYSIS

EXCITER

The exciter uses nine transistors and

two integrated circuits to drive the PA

assembly.

The exciter can be equipped with

up to eight Integrated Circuit Oscillator

Modules (ICOMs).

The ICOM crystal fre-

quency ranges from approximately 8,33 to

16.67 megahertz, and the crystal frequency

is multiplied three times (divided

by

four

r - - -

MOO

EXCITER

LBI-4896

and multiplied by 12 for a multiplication

factor of three) .

Audio, supply voltages and control

functions are connected from the system

board to the exciter board through P902.

Centralized metering jack Jl03 is pro-

vided for use with GE-Test Set Model

4EX3All or Test Kit 4EXSK12.

The test set

meters the modulator, multiplier and ampli-

fier stages.

ICOMS

Three different types of ICOMs are

available for use in the exciter.

Each of

the ICOMs contains a crystal-controlled

Colpitts oscillator, and two of the ICOMs

contain compensator ICs.

The different

ICOMs are:

•

•

•

5C-ICOM - contains an oscillator and a

5 part-per-million (±0.0005%) compen-

sator IC.

Provides compensation for

EC-ICOMs.

EC-ICOM- contains an oscillator only .

Requires external compensation from

a 5C-ICOM.

2C-ICOM - contains an oscillator and

a 2 PPM (±0.0002%) compensator IC.

Will not provide compensation for an

EC-ICOM .

I

ADJUST

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POWER

ADJUST

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AMPL-1

0102

BUFFER

0105

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•

AMPL-1

Q~OI

LIMITER

MOO

AMPL-2

1-------t-

CRI02

1------t"

0(03

CRI03

MULT-I

MULT-2

TRIPLER

DOUBLER

0106

0107

POWER AMP

PA

f----oo

DRIVER

r--

FINAL

0202

0203

1-----

f---.--

PHASE

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CVI02

C\1103

MULT-3

DOUBLER

0108

LOW

PASS

FILTER

Figure 1 - Transmitter Block Diagram

t--

r--

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AMPL-3

0104

AMPL-1

0109

t.Nr

SWITCH

K201

LIMITER

,,_.

CRI05

CRI06

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--1

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RC-2417A

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1

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