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Table 3-2. Crystal Frequencies and Operating Bands-continued - TM-11-5820-554-120030
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TM-11-5820-554-12 Radio Set AN/FRC-93(V)1 AN/FRC-93(V)2 AN/FRC-93(V)3. AN/FRC-93(V)4 AN/FRC-93(V)5 AN/FRC-93(V)6 AN/FRC-93(V)7 Manual
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Oscillators


TM 11-5820-554-12
Section IV. CIRCUIT FUNCTIONING
injection signal within the mixer and translates the
3-14. Block Diagram (fig. FO-1)
bandpass IF signal to the desired operating band.
c. RF and ALC Circuits. The output of transmit
The Collins KWM-2/2A is an ssb or a cw transceiver
mixer V6 is applied to receive/transmit amplifier V7.
operating in the range between 4.0 to 30 MHz.  It
The amplified output of V7 is applied to driver V8 to
consists of a double-conversion receiver and a double-
drive power amplifier V9 and V10. The output of the
conversion exciter-transmitter.  The transmitter and
power amplifier is fed to the antenna through contacts of
receiver circuits use common oscillators, a common
transmit-receive relay K3. Negative feedback from the
mechanical filter, and a common RF amplifier. The
pa plate circuit to driver V8 reduces distortion in the
transmitter low-frequency IF and the receiver low-
output signal.  Both the driver and pa stages are
frequency IF is 455 kHz. The high-frequency IF for both
neutralized to insure stability. When the RF driving
is 2.955 to 3.155 MHz. This a bandpass IF which
voltage to the pa becomes great enough that positive
accommodates the full 20-kHz bandwidth.
peaks drive the pa grid positive, the grids begin to draw
3-15. Transmitter Circuits
current and the signal is detected. This produces an
a. A,f Circuits. Microphone or phone patch is
audio envelope. The audio is rectified by ALC rectifier
connected to first transmit audio amplifier VIA,
V17A, which is connected to produce a negative d.c.
amplified and connected to second transmit audio
voltage. This voltage is filtered and is used to control
amplifier V11B. The output of V11B is coupled to third
the  gain  of  transmit  IF  amplifier  V4A  and
transmit audio amplifier V3A, amplified and coupled to
receiver/transmit RF amplifier V7. This system allows a
balanced modulator CR1 through CR4. In the TUNE,
high average level of modulation without overdriving
LOCK, and CW positions of the EMISSION switch, the
power amplifier V9 and V10 which would result in
output of tone oscillator V2B is applied to second
increased distortion.
transmit audio amplifier V11B.  The amplified tone
3-16. Receiver Circuits
oscillator signal at the output of V11B is applied to vox
a. RF Circuits. The signal input from the antenna is
amplifier V14B to activate the vox circuits in cw
applied through relay contacts to receive/transmit
operation. This signal is also applied to first receiver at
amplifier V7. The output of V7 is fed to first receive
amplifier V16A for cw monitoring.
mixer V13B.
b. Balanced Modulator and Low-Frequency IF
b. Receiver Mixers. The high-frequency injection
Circuits.  Audio output from third transmit audio
signal is fed to V13B. The difference product of the first
amplifier V3A and beat-frequency oscillator (bfo) V11A
mixer is applied to variable IF tuning T2. The output of
voltage are applied to the balanced modulator (CRT,
T2 in the range of 2.995 to 3.155 MHz is applied to
CR2, CR3, and CR4). Both upper and lower sideband
second receive mixer V17B. The vfo injection signal is
outputs from the balanced modulator are applied to
applied to V17B. The 455-kHz difference product is
transmit IF amplifier V4A.  The output from the IF
applied to mechanical filter FL1.
amplifier is applied to mechanical filter FL1.  The
c. IF Circuits. The output from FL1 is applied to
passband of FL1 is centered at 455 kHz. This passes
first receive IF amplifier V1B. The output of V1B is
either the upper or lower sideband depending upon the
applied to second receive IF amplifier V3B and to the
sideband selected when the EMISSION switch connects
age detector.  The output of V3B is fed to product
the bfo upper or lower sideband crystal. The single-
detector V15B. The beat-frequency oscillator signal is
sideband output of FL1 is applied to first transmit mixer
applied to the product detector, and the product of the
V5.  The mixer cancels the vfo signal energy and
mixing is the detected audio signal. The output of the
translates the 455-kHz single-sideband signal from the
age rectifier circuit is applied to the two receive IF
balanced modulator to a 2.955- to 3.155 MHz single-
amplifiers and to receive/transmit RF amplifier V7. This
sideband signal. The output of the first transmit mixer
avc voltage controls the gain of the receiver and
is applied through variable IF tuning T2 to second
prevents overloading.
transmit mixer V6. The high-frequency injection energy
d. If Circuits. The output from the product detector is
from crystal oscillator V13 A is also applied to mixer
applied to first audio amplifier V16A. The amplified
V6.  This arrangement cancels the high-frequency
audio  output  of  V16A  is  applied  to  second
3-15


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