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Figure 15. Audio output circuits, schematic diagram
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TM-11-5820-222-35 Radio Sets AN/VRC-24 and AN/TRC-68 Manual
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Figure 16. RT unit, transmitting signal path, block diagram


TRANSMITTER THEORY
Section I. TRANSMITTER SIGNAL PATH
as described in paragraph 8 c, ex-
46. Common Purpose Stages
cept that when injection relay K102
Several stages in this equipment are used
is energized, the uhf injection unit
in both the receive and transmit functions.
output is applied to second trans-
Where the circuit remains identical (ex-
mitter mixer V101 instead of first
cept for some switch position), reference
receiver mixer V104.
is made to the illustrations in the receiver
c. Rf Amplifier Section.
section of this manual. Refer to figure 16,
(1) The 20.0 to 29.9-if. signal and the
the transmitting path block diagram, which
200- to 370-mc uhf injection signal
shows the order in which the stages are
are heterodyned by second trans-
discussed in this chapter.
mitter mixer V101 to produce an
rf carrier which can be varied from
47. Transmitter Block Diagram
220.0 to 399.9 mc. (The first 5-mc
band is not considered to be within
a. General. The signa1 path for the
the useful range of the rt unit.)
transmit function of the rt unit is shown in
First  and  second  rf  amplifiers
the block diagram and is discussed in b
V102 and V103 and third trans-
through e below. The block diagram shows
mitter rf amplifier V104 provide
the positions of the relays in the signal
three stages of rf amplification.
path. When the rt unit is turned on and the
(2) The output of V104 is applied to
handset or microphone push-to-talk switch
transmitter driver V105. The out-
is operated, the relays energize and the
p u t of V105 drives transmitter
rt unit operates as a transmitter.
power amplifier V106. The B+ sup-
b. Signal Generating Section.
p l i e d to both transmitter driver
(1) On transmit, third oscillator
V105 and transmitter power am-
V401B generates a signal from 3.0
plifier V106 is modulated by audio
to 3.9 mc that is coupled to trans-
signals from audio output trans-
mitter buffer amplifier V401A. The
former T802.
amplified output of V401A is ap-
d. Audio Amplifier Section. Audio pre-
p l i e d through bandpass filters
a m p l i f i e r V803 receives audio signals
Z 4 0 3 , Z402, and Z401 to first
from the local or remote microphone, or
transmitter mixer V304.
from the external retransmit equipment.
( 2 ) The 3.0- to 3.9-mc signal is heter-
The audio input is applied to audio pream-
odyned with the 17.0- to 26.0-mc
plifier V803 when squelch relay K801 is
signal from second oscillator V305
deenergized and the NOR-BB switch is set
i n first transmitter mixer V304.
on NOR. Audio signals are amplified and
The sum frequency, 20.0 to 29.9
coupled to modulator driver V804. Encoded
mc, is amplified by first and second
broadband signals are applied to audio
if. amplifiers V301 and V302. The
preamplifier V803 when the broadband
amplified 20.0- to 29.9-mc if. sig-
s w i t c h is set for broadband operation.
n a l is coupled to second trans-
e. Modulator and Output Stages.
mitter mixer V101 and heterodyned
(1) Modulator driver V804 amplifies
with the 200- to 370-mc signal from
the audio signals to drive trans-
the uhf injection subunit.
mitter  modulator  stages  V805,
( 3 ) The uhf injection system operates


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