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

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DESCRIPTION
Transmitter Types KT-56-A, C, KT-57-A,
C
&
KT-58-A, C are crystal-controlled, phase
modulated transmitters designed for one-
through four-frequency operation in the 25
to 50 megahertz band. The solid state
transmitter utilizes both integrated cir-
cuits (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, filter
and antenna switch.
CIRCUIT ANALYSIS
EXCITER
The exciter uses nine transistors and
two integrated circuits to drive the PA as-
sembly. The exciter can be equipped with up
to four Integrated Circuit Oscillator Mod-
ules (ICOMs). The !COM crystal frequency
ranges from approximately 8,33 to 16.67 meg-
ahertz, and the crystal frequency is multi-
plied three times (divided by four and
multiplied by 12 for a multiplication of
three).
EXCITER
I
MOD
~ADJUST
I
r
-1
~
H
MOD
I
AUDIO
PHASE
AMPL-1
r------1
LIMITER
MOD
0102
CRI02
Ul02
CVIOI CRI03
I
I
_ _ _j
~
FREO
MULT-I
Fl
t---r1
BUFF~R
~
DIVIDER
BUFFER
r----
TRIPLER
YIOI 0101
(+4)
0105 0106
I
UIOI
I
I
I
--- ---
LBI-4732
__ Audio, supply voltages and control
functions are connected through P902 .
Centralized metering jack Jl03 is pro-
vided for use with GE Test Set Model 4EX3All
or Test Kit 4EX3Kl2. The test set meters
the modulator, multiplier and amplifier
stages.
ICOMS
Three different types of ICOMs are
available for use in the exciter.
Ea~h
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%) compensa-
tor 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.
The ICOMs are enclosed in an RF shield-
ed can with the type !COM (5C-ICOM, EC-ICOM
or 2C-ICOM) printed on the top of the can.
Access to the oscillator trimmer is obtained
l
MOD
PHASE
f-----.1
AMPL-2
f-----.1
MOD
0103 CVI02
CVI03
MULT-2
MULT-3
f----
DOUBLER
--
DOUBLER
0107
OIOB
--- ---
1----i
r----
MOO
AMPL-3
0104
AMPL-1
0109
I
I
I
HLIMITER
CRI05
CRI()6
I
I
--- ---
~-- -~
I
I
F2 •
-1 I
POWER
POWER AMP
~
I
I
Yl02
I
ADJUST
0204-0210
~-
:
I
I
I
I
~---.
I
PA
I
Fe
1-_j
AMPL-1
t-----
DRIVER
I - -
FINAL
f----
I
YIOB
0201
0202
0203
~--.J
Figure 1 - Transmitter Block Diagram
LOW
ANT
PASS
I - -
SWITCH
FILTER K201
RC-265B
I
I
I
_j
1