(1) Receiver-transmitter function switch set
b. Power Distribution.
(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
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
applied through the RF-IF amplifiers and the
discriminator circuits to receiver audio amplifier
(3) In the receiver-transmitter, the follow-
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-
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
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,
System Power Distribution, Including
transmitting amplifier, and the power amplifier
Crew-member Control Boxes
(P.A.) stages to the antenna for transmission to
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
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-