Simplified Transmitting Signal Path

range without disturbing the preset chan-

the frequency range of 225.0 to 399.9 mc.

nels.

The input signals are heterodyned with the

200- to 370-mc signal supplied by the

b. Frequency Selection.

ultrahigh frequency (uhf) injection subunit

(1) The frequency selector subunit in-

to produce a 20.0 to 29.9-mc first inter-

cludes four automatic positioners:

mediate frequency (if.) signal. The 20.0 to

a 20-position channel selector; an

29.9-mc if. signal is amplified and heter-

18-position, 10-mc selector; a 10-

odyned with a 17.0 to 26.0-mc signal in the

position, 1.0-mc selector; and a

first if. amplifier subunit to produce a 3.0

10-position, 0.1-mc selector. The

to 3.9-mc if. signal. The 3.0- 3.9-mc if.

20-position, channel selector auto-

signal is heterodyned again to produce a

matic positioner, controlled by the

500-kilocycle (kc) if. signal. The 500-kc

setting of the CHAN SEL selector

signal is amplified by the 500-kc if. am-

switch on the front panel to the

plifiers and demodulated. The audio sig-

CHANNEL selector switch on the

nals are amplified in the 500-kc if. ampli-

radio set control, positions a chan-

fier and audio amplifier and modulator

nel selector memory drum to

subunits and applied to the local, remote,

select the desired channel.

and fixed level outputs or to the broadband

equipment. Decoded signals from the

(2) The 10.0-, 1.0-, and 0.1-mc auto-

broadband equipment are returned to the

matic positioners drive seeking

audio amplifier and modulator for ampli-

switches which select the fre-

fication before being applied to local, re-

quencies preset on the memory

mote, or fixed level audio outputs.

drum or on the MANUAL FRE-

QUENCY controls. The 10.0 -,1.0-,

5. Simplified Transmitting Signal Path

and 0.1-mc automatic positioners

(fig. 2)

also drive five tuning shafts

through a series of gear trains.

The rt units transmit am. radiofrequency

(rf) signals in the frequency range of 225.0

(3) The frequency selector shafts are

to 399.9 mc. During transmission, the first

coupled to the tuning shafts within

and the 3.0- to 3.9-mc if. amplifier sub-

the rf and power amplifier, the uhf

units function as signal generators. The

injection subunit, and the first and

3.0- to 3.9-mc signal is heterodyned with

3.0- to 3.9-mc if. amplifier sub-

a 17.0- to 26.0-mc signal from the first

units.

if. amplifier subunit to produce a 20.0- to

(4) When each seeking switch reaches

29.9-mc signal. This signal is heterodyned

its proper position, the corre-

with a 200- to 370-mc signal from the uhf

sponding automatic positioner

injection subunit to produce an rf carrier

stops. When all automatic posi-

that can be varied from 225.0 to 399.9 mc.

tioners have stopped, the rt unit is

The rf carrier signal is amplitude modu-

ready for operation on the selected

lated by audiofrequencies from the audio

channel frequency.

amplifier and modulator subunit and cou-

pled to the uhf antenna.

7. Power Supplies

6. Frequency Selector System

a. Radio Set AN/VRC-24 Power Supply.

a. General. The frequency range of the

The internal power supply of Radio Set AN/

rt units is covered by 1,750 crystal-con-

VRC-24 consists of Dynamotor DY-151/U

trolled channel frequencies in 0.1-mc

and appropriate filters which provide the

steps. Nineteen channels can be preset for

+125-, +300-, and -30-volt direct current

automatic selection from the front panel

(dc) operating voltages. Dynamotor DY-

or from the radio set control. A manual

151/U operates on an input voltage of 26.4-

system permits selection of any channel

volt dc. Relay and filament voltages are

frequency within the 225.0- to 399.9-mc

supplied directly from the input voltage.