General Description-continued

TM 11-5820-509-35

oscillator is coarse-tuned in ten 1-MHz stems by the

receive rf from the antenna system passes through the

whole megahertz control knob on the front panel of

t/r relay directly to the rf amplifier stages. Tuned circuits

RT671/PRC-47. Fine tuning is accomplished by varying

in these stages reject unwanted signals that may enter

the vfo output inductor with the 10-kHz and the 100-kHz

the antenna system, and select only the desired band of

frequency control knobs, or by the application of a dc

signals for amplification before routing them to the

error voltage to the frequency determining circuits by

receiver mixer. In the receiver mixer, the rf signal is

the discriminator of Oscillator Control C-4311/PRC-47

heterodyned with the 2.5 to 12.499-MHz hf oscillator

IA7).

This discriminator is part of a closed-loop

signal to produce an intermediate frequency output near

frequency control system that compares the vfo output

500-kHz. The if. amplifier and bandpass filter circuits

with crystal-controlled reference oscillator frequencies

used for transmitting are also used in the receive mode.

and then automatically adjusts the vfo output frequency

In these circuits the incoming signal is amplified while

to synchronize it with the crystal standard frequencies.

undesired adjacent-channel and image signals are

The crystal oscillators are adjustable in four decades:

attenuated before the if. signal is applied to the product

whole megahertz step, 100-kHz steps, 10-kHz steps,

detector. The output of the product detector is the

and 1-kHz steps. The whole megahertz and 100kHz

demodulated single-sideband receive if. signal. This

signals are derived from a common highly stabilized

audio output is filtered and then amplified by the

crystal-controlled source in Radio Frequency Oscillator

receiver amplifier and audio output amplifier circuits

0-1032/PRC-47 (A6). This 3-MHz primary signal is first

before being applied to the earphone or other connected

divided by six to obtain the 500-kHz standard signal

audio output device.

used by the receiver-transmitter circuits and by the I-

MHz pulse generator in the CV-1377A/PRC-47 (A3).

c. The frequency control circuits of Radio Set

Then this 500-kHz output is further divided by five to

AN/PRC-47 are shown in figure 2-3. The hf oscillator

obtain the 100-kHz signal used in the 100kHz pulse

signal for both the transmit and receive functions is

generator circuit of oscillator control

obtained from the variable frequency oscillator (vfo) of

Signal Data Translator CV1377A/PRC-47 (A3). This

2-5