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Page Title:
Section II. OVERALL FUNCTIONAL DESCRIPTION |
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|  TM 11-5820-919-40-1
SECTION II
OVERALL FUNCTIONAL DESCRIPTION
2-18.
GENERAL.
2-23.
Mode Selection. The MODE switch
selects either voice transmit (V-TR),
voice receive (V-RCV), data transmit
2-19. RADIO SET. The radio set con-
(D-TR), or data receive (D-RCV). The
sists of three major assemblies:
Mode Select signals are used by the
modulator/demodulator to control the
Receiver/exciter (A1)
1.
processing of the transmit/receive radio
frequency (Xmt/Rcv RF). In the voice
Amplifier/coupler (A2)
2.
mode, the microphone input impedance is
150 ohms and the VOLUME control adjusts
Battery pack
3.
the level of the Rcv Audio. In the data
mode, the input impedance is changed to
The receiver/exciter contains five mod-
600 ohms, which is compatible with stan-
ules: (1) control panel, (2) synthe-
dard data systems. The VOLUME control
sizer, (3) modulator/demodulator, (4)
is also disabled so that a constant
harmonic filter, and (5) the power
receive level is maintained. In addi-
supply.
The amplifier/coupler contains
tion, the receiver agc release time
the power amplifier and antenna tuner
constant is shortened to reduce the
modules. The battery pack provides the
receive response time to incoming data.
radio set with the +28v (nominal) dc
power.
2-24. Sideband Selection. The SB
switch selects either upper sideband
2-20.
RECEIVER/EXCITER (Figure 2-2).
(USB) or lower sideband(LSB) of the
radio frequency. The Sideband Select
2-21. CONTROL PANEL. The control panel
signals are sent to the synthesizer.
provides operational control of the
The synthesizer sends either 70 MHz to
radio set and couples transmit/receive
the modulator/demodulator if USB is
audio signals between the audio devices
selected or 80 MHz if LSB is selected.
in use by the operator and the radio set.
The control panel contains the FREQUENCY
2-25. Volume Control. The VOLUME con-
KHZ (frequency select) switches, MODE
trol is used to control the Rcv Audio
select switch, SB (sideband) select
level from the modulator/demodulator.
switch, VOLUME control, LIGHT switch,
and audio connectors.
2-26. SYNTHESIZER. The synthesizer
generates the 5 MHz, 70 (USB) or 80
2-22. Frequency Selection. The FRE-
(LSB) MHz, and 77-105 MHz LO signals.
QUENCY KHZ switches select the operating
The exact frequency of the 77-105 MHz
frequency of the radio set (2,000 thru
LO is 75 MHz plus the control panel
29,999 kHz). The frequency select
frequency. The LO signals are used by
switches send Frequency Select signals
the modulator/demodulator in the proc-
(logic data) to the synthesizer for use
essing of transmit/receive signals.
in determining the frequency of the
The synthesizer also generates a l-kHz
77105 MHz LO signal. The Frequency
tone which is used by the modulator/
Select signals are also used by the
demodulator to develop a cw key tone.
The Filter Select signal from the fre-
quency select switches is used by the
2-27. MODULATOR/DEMODULATOR . In trans-
harmonic filter to select the bandpass
mit operation the modulator/demodulator
filter corresponding to the selected
converts the Xmt Audio into two succes-
frequency.
sive intermediate frequencies and then
2-7
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