The power supply circuits of the AN/PRC47

TM 11-5820-509-35

power source. Interlocking is provided so that alternate

generator circuit of oscillator control (A7). This circuit

source input circuits are disconnected. When the

generates a 100-kHz pulse-train and then converts it to

receive mode is selected, all necessary voltages for the

a sine wave at any single 100-kHz frequency step

radio set are provided by the low-voltage filter regulator

between 1.8and 0.9 MHz.

The selected whole

circuit of Power Supply PP-3518/PRC47 (A5). This

megahertz output of the 5to 14-MHz amplifier in CV-

subassembly filters and regulates the 26.5-volt dc

1377A/PRC-47 (A3) is combine with the selected 100-

primary power when the dc mains are connected, but

kHz output of the 1.8 to 0.9-MHz circuits in a mixer

when the 115-volt, 400-Hz primary power source is

whose output is the difference between these two input

attached, a portion of this voltage is rectified by the low-

frequencies. The resulting reference signal has a range

voltage circuits and then smoothed by the filter-regulator

from 3.2 to 13.1MHz in 100-kHz steps, and it is combine

before application to the circuits in the modules of the

with the 2.5to 12.499-MHz vfo signal in a second mixer

equipment. When the transmit mode is enabled, high-

circuit. The resulting 700to 601-kHz signal represents

voltage power supply circuits provide heater. bias, and

the hf oscillator output with an accrued frequency error.

plate power for the vacuum tubes and bias voltages for

Two crystal oscillators in C-4311/PRC-47 (A7) provide

the transistorized circuits of the radio set. The high-

reference signals that are combine also in a mixer.

voltage power supply circuits are enabled by operation

These oscillators are adjusted by the gear-train

of the push-to-talk (ptt) switch on the operator's handset,

associated with the 1-kHz and the 10-kHz frequency

by placing the CW-FSK/VOICE switch on the front of

dials of the KILOCYCLES indicator on the front panel of

RT-671/PRC-47 to CW-FSK, or by setting the OPR-

RT-671/PRC-47.

The output of this third mixer

TUNE switch on the front of RT-671/PRC-47 to TUNE.

represents the desired channel selection in 1-kHz steps,

When the 115-volt ac primary power mains are

and this frequency is combined in the discriminator

connected, operation of the high-voltage transformer

circuit with the output of the second mixer to obtain an

and rectifier-filter circuits is conventional. A multiple-

error voltage proportional to the vfo error signal. The

secondary high-voltage transformer provides ac power

output of the discriminator controls the vfo and returns it

to the several rectifier-filter circuits that distribute the

to the desired operating frequency.

required transmitter voltages. If the 26.5-volt dc primary

power source is connected, however. a portion of this

d. The power supply circuits of the AN/PRC47 are

power is applied to a 400-Hz power oscillator on the

shown in figure 2-4. These circuits obtain primary power

main chassis of RT-671/PRC-47. This circuit performs

from either the 115-volt, 400-Hz ac mains or from a 26.5

the normal inverter function and generates a square-

volt dc primary power source similar to Storage Battery

wave voltage whose output amplitude is approximately

BB-451/U. The appropriate circuit within the power

26.5 volts at 400 Hz. The square-wave voltage from

supply is automatically selected when the power cable is

this power oscillator is applied to an appropriate primary

attached to the front panel connector of the radio set.

winding on the high-voltage transformer and suitable

Operation of the POWER-LIGHTS switch on the front of

output voltages are obtained from the connected

RT-671/PRC-47 to the POWER ON position causes the

rectifier-filter circuits.

appropriate power control relay to operate and connect

the appropriate input circuit to the selected primary

2-7