Transmitter, Radio T-1054 (P) A/GRC-144(V) Modulator 1A8 Functional Block Diagram Description

TM 11-5820-695-35

frequency of the 150 MHz oscillator in 1A8. The traffic

tor switch. Also, the afc level at the output of the limiter

stages in electronic frequency control 1A7 is applied to

input signal (combined data and orderwire signal) is

applied to baseband amplifier Q101-Q103 through

the meter selector switch through meter circuit 1A7CR9.

Any one of the above signals may be monitored by

BANDSET switches S102 and S101. These switches

are set according to the operating frequency, as

setting the meter selector switch to the desired position.

explained in paragraph 2-35.1. Front panel variable

resistor R149 is used to adjust the input level to the

2-10.1

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

baseband amplifier (transmitter fm deviation). The

Modulator 1A8 Functional Block Diagram

amplified traffic signal is then applied to 150 MHz vco

Description (fig. 5-11.1)

Q1. The 150 MHz vco uses varactor diodes to control

The modulator circuits in Transmitter, Radio T-

the output frequency. A positive going traffic signal

1054(P)A/{IRC-144(V) are basic all the same as those in

deviates the vco toward a lower frequency and a

Transmitter, Radio T-1054(P)/GRC-144(V) (para 2-10).

negative going traffic signal deviates the vco toward a

The same functions are performed and the circuits are

higher frequency. The vco's center frequency can be

the same except as noted below.

adjusted with front panel variable capacitor C114. The

a. Input Circuits. In digital orderwire mode, the

150 MHz frequency modulated output of the vco is

combined data/digital orderwire signal is applied to

applied to limiter amplifier stages Q104 to Q106 and

attenuator assembly 1A3, and the PH NTWK switch is in

Q108 through buffer amplifier Q109 which isolates the

NORMAL position. The signal is coupled through the

vco from the amplifier stages. The amplified frequency

attenuator to AF-RF amplifier 1A4. Since there is no

modulated 150 MHz signal is applied through matching

analog orderwire signal, the input from orderwire

pad R154-R156 to frequency mixer 1A9.

assembly 1A13 is grounded by OW SEL switch in the

DVOW position. In analog orderwire mode, the PH

NTWK switch is in the IN position and the data (only)

c. Electronic Frequency Control 1A7.

Refer to

signal is coupled through the phase shift network to AF-

paragraph 2-10c.

RF amplifier 1A4. The OW SEL switch is in AVW

d. Meter Circuits.

position and the analog orderwire signal from orderwire

assembly lA13 is coupled through an attenuator

(1) The orderwire metering circuit in

according to the position of DATA RATE switch. For

attenuator assembly IA3 provides an output to the meter

higher data rates, a different attenuator assembly is

selector switch on meter panel assembly 1A15A8. The

used for 1A3 and LPF 1A6 is replaced by a cable, as

orderwire signal level may be monitored by setting the

shown in figure 5-11.1.

meter selector switch to the OW TEST position.

b. Radio Transmitter Modulator 1A8.

Radio

(2) Various signals from radio transmitter

transmitter modulator 1A8 receives the combined data

modulator 1A8 and electronic frequency control 1A7 are

and orderwire signal and produces a frequency

applied to the meter selector switch on meter panel

modulated 150 MHz output which is applied to

assembly 1A15A8. The traffic input to lA8 is applied

transmitter frequency mixer stage 1A9. A sample of the

through emitter follower Ql10 to attenuator assembly

frequency modulated output is fed back from 1A8 to

1A3 and then through alarm monitor 1A5 to meter panel

electronic frequency control 1A7 which produces an afc

assembly 1A15A8.

signal to stabilize the TM 11-5820-695-35 center

Change 6 2-29