Receive Signal Path

TM 11-5820-509-35

Figure 2-4. Power Supply Circuits, Block Diagram.

receiver mixer Q11 with the output of Q10. The

2-5. Receive Signal Path

difference between these two signals, approximately

(fig. 7-2)

500 kHz, is applied to follower Q9 and routed to the if.

a. In the receive mode, the 2.0to 11.999-MHz rf

amplifier circuits of amplifier-modulator A2.

After

signal from the antenna system is routed through the

amplification by A2Q2, the if. signal is routed through

normally-closed contacts of t/r relay K101 in the power

bandpass filter FL1 where the if. carrier signal and the

amplifier compartment to receiver antenna relay K5 on

undesired sideband are greatly attenuated. Following

the Main chassis of the receiver-transmitter. Both of

additional amplification by if. amplifiers Q3 through Q5,

these relays are deenergized in the receive mode, but

this signal is demodulated by the product detector

are energized by the voice-operated-transmit (vox)

circuit.

circuits during transmitter operation. The receive rf

signals from the normally closed contacts of receiver

antenna relay K5 pass through the tuned circuits of

c. The audio component of the if. signal is

signal data translator A3 and are amplified by rf

extracted by mixing the if. signal with a carrier injection

amplifiers V1 and V2. These stages are also used tc

signal (500-kHz standard) at the intermediate frequency.

amplify transmit rf signals when the transmit mode is

The output of the product detector is then passed

selected, and are tuned to the operating frequency

through a low-pass filter to remove undesired

selected by the frequency control knobs on the front

frequencies caused by mixing and then amplified by

panel of RT671/PRC-47. The additional selectivity

driver stage Q10 and audio output amplifier Q11WQ12X

provided by these tuned circuits restricts the signals

in audio frequency amplifier A1. This amplified audio

applied to the rf amplifier input to those that are on, or

signal is applied to the corrected audio output device

very near, the selected operating channel.

through front panel VOLUME control R11-R12. Once

b. Relay A3K1 is deenergized during receiver

the average audio output level has been established by

operation and its contacts route the amplified rf signal

the setting of the VOLUME control. automatic gain

from the second rf amplifier (V2) to follower Q1O.

control (agc) circuits in audio frequency amplifier A1

(During transmit periods. A3K 1 is energized and

maintain the output level relatively constant despite

capacitor C187 is connected to the output of V2.) The

fading signal conditions. The +agc voltage' from agc

hf oscillator signal from the frequency control circuits is

amplifier Q9 is applied to if. amplifiers Q2 and Q3 while

isolated by follower 24 Q12 and is then mixed in

the -agc output of detector CR12-CR13 is applied to

2-8