Transmitter, Radio T-1054(P)/ GRC-144(V) Modulator Circuits Functional Block Diagram Description

TM 11-6820-695-35

695-35 signal phase shift requirement of Radio Set AN/

1A13A2. OR gate A triggers multivibrator circuit Q1, Q2

GRC-144 is 37 degrees at 300 Hz). Af-rf amplifier 1A4

and Q3 into operation. The multivibrator alternately

provides a maximum gain of 25 db. The amplifier

connects ground to the 1.1 kHz oscillator inputs. The

comprised of stages Q1, Q2, Q3 is basically a shunt

1.6 kHz oscillator is located on 1A13A6. The alternating

feedback amplifier. The TRAFFIC LEVEL ADJ control

output of each oscillator is coupled through the TEST

at the input to the amplifier allows the gain to be

TONE and RING switches and applied to emitter

adjusted from its maximum value to zero.

followers Q4 and Q5 and speaker amplifier A2 on

1A13A2. The output of A2 is applied to the monitor

(2) The orderwire input from orderwire

circuit amplifier A2 through switch section SlA-r12.

assembly 1A13 is applied to the 48 channel attenuator

Monitor circuit amplifier A2 will provide an output to

and metering circuit through the input attenuator circuit

extinguish the MODULE TEST indicator. Alarm OR

and the 48/96 channel selector switch. The OW LEVEL

gate B turns off transistor switch Q6 on l'A13A2, thereby

ADJUST control in the input attenuator circuit and the

removing the operating voltage from CNTRL IALARM

4.8 channel attenuator circuit are used to maintain the

indicator on meter panel assembly 1,A15A8. Removing

orderwire signal level within 15 to 20 percent of the pcm

the voltage changes the lamp indication from green to

signal level. The orderwire signal level is detected in

red for alarm condition. Emitter follower Q4 applies the

the 48 channel metering circuit for application to the

1.1/1.6 kHz tone to meter panel assembly 1A15A8 for

meter selector switch. The 48/96 channel selector

an audible alarm.

switch is placed in the 48 CH position for all modes of

operation. (The 96 CH selector switch position and

2-10.

Transmitter, Radio T-1054(P)/ GRC-144(V)

associated attenuator and metering circuits are provided

Modulator Circuits Functional Block Diagram

for future applications of Radio Set AN/GRC-144.) The

Description (fig. 5-11)

pcm output signal from af-rf amplifier 1A4 and the

orderwire signal are connected together at the output of

The modulator circuits consist of input circuits, radio

af-rf amplifier 1A4 and form a combined signal (pcm

transmitter modulator 1A8, and electronic frequency

and orderwire) input to 4.5 MHz low-pass filter 1,A6.

control 1A7. The input circuits combine the pcm and

The 4.5 MHz lowpass filter passes the combined signal

orderwire signals at the appropriate signal levels. The

to radio transmitter modulator 1A8 and, together with

composite signal is applied to radio transmitter

other filters in the radio set, provides the required

modulator llA8 and modulates a 160 MHz oscillator in

shaping.

1A8. The frequency modulated 1150 MHz output is

b. Radio Transmitter Modulator IA8.

Radio

applied to transmitter frequency mixer stage 1A9. A

transmitter modulator 1A8 receives the combined pcm

sample of the frequency modulated output is fed back

and orderwire signal and produces a frequency

from radio transmitter modulator 1A8 to electronic

modulated 1'50 MHz output which is applied to

frequency control 1A7 which produces an automatic

transmitter frequency mixer stage 11A9. A sample of

frequency control (afc) signal to stabilize the center

the frequency modulated output is fed back from 1AS to

frequency of the 150 MHz oscillator in 1A8.

electronic frequency control 1A7 which produces an afc

a. Input Circuits. The input circuits consist of

signal to stabilize the center frequency of the 160 MHz

attenuator assembly 1A3, af-rf amplifier 1A4, and 4.5

oscillator in 1AS.

MHz low-pass filter 1A6.

(1) The traffic input signal (combined pcm

(1) The pcm input from digital data modem

and orderwire signal) is applied to operational amplifier

1A12 is applied to pcm attenuator and phase shift

Al (integrated circuit). Front panel variable resistor R2

network (R1-R5, C1, C2) in attenuator assembly 1A3.

is used to adjust the input level to the amplifier Al

The attenuator and phase shift network provides a pcm

(transmitter fm deviation). The amplifier traffic signal is

signal phase shift of 21 degrees at 300 Hz and

then applied to 150 MHz vco Q1. The 1650 MHz vco

attenuates the signal to the proper level for application

uses varactor diodes to control the output frequency. A

to af-rf amplifier 1Au4. To maintain separation between

positive going traffic signal deviates the vco toward a

pcm and orderwire signals, a 21-degree phase shift of

lower frequency and a negative going traffic signal

the transmitter signals is required (the receiver signals

deviates the vco toward a higher

phase shift is 16 degrees and the overall TM 11-5820-

Change 6 2-27