System Power Distribution, Including Crew-member Control Boxes

TM 11-5820-498-35

(1) Receiver-transmitter function switch set

b. Power Distribution.

to ON.

(1) Power from the battery source is ap-

p l i e d through the MT1029/VRC and the

(a) A signal received

AM2060(*)/GRC PWR switch CB1 to audio am-

applied through the RF-IF amplifiers and discri-

plifiers Q1 and Q2, and to regulator amplifiers Q3

minator circuits to receiver audio amplifier

and Q4. The dc power is also applied through

A25/A55.

ANT. FREQ. CONTROL switch S2 to the control

(b) From the A25/A55, the speech signal

circuits of the antenna matching unit

are applied as follows:

(MX-2799/VRC or MX-6707/VRC).

1. To the audio accessory earphone.

(2) From the AM-2060(*)/GRC, the dc op-

2. Through AM-2060(*)/GRC audio

erating voltages are applied to the receiver-trans-

amplifiers Q1 and Q2 to the loudspeaker.

mitter: 13 volts for both receiver-transmitters

(2) Receiver-transmitter function switch set

(RT-505/PRC-25 and RT-841/PRC-77), and 3

to SQUELCH. When the function switch is set to

and 2.6 volts for the RT-505/PRC-25 only.

SQUELCH, signals received at the antenna must

c. Radio Transmission. When the push-to-talk

contain a 150-Hz squelch tone. Until the 150-Hz

switch in the audio accessory is operated to radio

tone is received, receiver-transmitter relay K3 is

position, the following circuit operations occur.

unoperated. Relay K3 provides a short circuit to

(1) The audio accessory push-to-talk switch

ground through K3 contacts and function switch

provides a ground through receiver-transmitter

S1 for the output transformer in A25/A55. Thus,

relays K1 and K2 for the 13 volts supplied by Q3

the FM rushing noise is not heard in the audio

and Q4 in the AM-2060(*)/GRC.

accessory earphones or the loudspeaker.

(2) In the AM-2060(*)/GRC, K1 also oper-

ates and disconnects the loudspeaker from the

(a) Signals received at the antenna are

audio circuit.

applied through the RF-IF amplifiers and the

discriminator circuits to receiver audio amplifier

(3) In the receiver-transmitter, the follow-

A25/A55.

ing actions occur:

(b) From the discriminator, the 150-H

(a) Relay K3 remains unoperated. Relays

squelch signal is applied to squelch relay contr

K1 and K2 operate to apply power to the trans-

A24/A54.

mitter circuits of the receiver-transmitter. In the

(c) A24/A54 then provides a closed cir-

RT-505/PRC-25, K2 applies power to the fila-

cuit to operate relay K3. When K3 operates, it re-

ment of the power amplifier V1.

moves the short from the output transformer in

NOTE

A25/A55.

Relay K1 in the AM-2060(*)/GRC also oper-

(d) Speech signals are now applied from

ates and disconnects the loudspeaker from

the output transformer in A25/A55 to the audio

the output of Q1 and Q2. This operation

accessory earphones. The speech signal is also ap-

prevents sound feedback between the loud-

plied through the AM2060(*)/GRC audio ampli-

speaker and the audio accessory microphone.

fier Q1 and Q2 to the loudspeaker.

(b) Speech signals from the audio acces-

sory now applied through speech amplifier A22,

2-3.

System Power Distribution, Including

transmitting amplifier, and the power amplifier

Crew-member Control Boxes

(P.A.) stages to the antenna for transmission to

(fig. 4-4)

the distant radio station.

The distribution of power to operate the radio,

(c) Sidetone of the speech amplifier is ap-

AM2060(*)/GRC, and the crewmember control

plied from speech amplifier A22 through receiver

boxes is controlled from the AM1780/VRC.

audio amplifier A25/A55 to the audio accessory

Whenever the intercom equipment is connected to

earphones.

the radio and the intercom system, the link in the

d. Radio Reception. For radio reception, the

MT1029/GRC must be connected for remo

push-to-talk switch of the audio accessory is uno-

power control operation as shown in figure 4-4.

perated. The following circuit operations occur

The setting of the AM-1780/VRC MAIN PWR

when a signal is received from the distant radio

switch determines the path of the power distribu-

station. Receiver-transmitter relays K1, K2, and

tion from the MT-1029/VRC. The charts in a and

K3, and the AM2060(*)/GRC relay K1 is uno-

b below trace the distribution of power through-

perated.

2-2