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

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DESCRIPTION
MASTR II transmitters are crystal-con-
trolled 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 freq-
uency ranges from approximately 8,33 to
16,67 megahertz, and the crystal frequency
is multiplied three times (divided by four
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EXCITER
MOD
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~-fOJUST
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Ehf"'~
QIQJ
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POWER
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F2
~-~ POWER
ADJUST
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0211 ·Q217
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I F8
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AMPL·! DRIVER
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YIOB
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0204 0205
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XTAL FREQ•
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LBI-4898
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 4EX8Kl2. The test set meters
the modulator, multiplier and amplifier
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:
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AMP
5C-ICOM - contains an oscillator and
a 5 part-per-million (±0.0005%) com-
pensator 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 •
2506A
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Figure 1 - Transmitter Block Diagram
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