Chapter 4. PRINCIPLES OF OPERATION - TM-11-5820-815-140047

TO 31R2-2GRC171-2

TM 11-5820-815-14

NAVELEX 0967-LP-544-5010

CHAPTER 4

PRINCIPLES OF OPERATION

4-1. INTRODUCTION.

cuits. Section III covers operating theory of mechani- cal

assemblies. Refer to TO 31-1-141 for principles of

4-2. This chapter contains a discussion of Radio Set

operation of basic electronic circuits. Unless otherwise

AN/GRC-171 based on functional block diagrams,

indicated, the discussion and figures in this chapter

simplified schematic diagrams, and complete sche-

cover the latest effectivities. Where differences in

matic diagrams of the equipment. Section I covers the

effectivities are minor (value changes, slight changes in

AN/GRC-171 on an overall functional basis. Sec- tion II

circuit configuration, etc), they are not discussed.

provides detailed coverage of electronic cir-

SECTION I

FUNCTIONAL SYSTEM OPERATION

4-3. GENERAL.

section (upper half of figure FO-3).

Through a

transmit/receive switch, the transmitter and receiver

4-4. This section discusses the overall system opera-

share a common rf filter at the antenna port of the

tion of Radio Set AN/GRC-171 followed by a discus- sion

receiver-transmitter. The rf filter is tuned to the radio

of the transmit, receive, and power distribution functions.

control frequency so that it passes only the desired

Also discussed is system keying and dis- able circuits

transmit and receive signals and rejects all other signals.

along with frequency control circuits. Figure FO-3 shows

With the exception of the rf filter, the only other common

an overall block diagram of the AN/GRC-171. Figure

circuits between the receiver section and transmitter

FO-16 shows transmit signal flow of the transmitter

section are frequency control, key line, and power supply

section, and figure FO-15 shows receive signal flow of

voltage. Frequency control is provided by a phase-

the receiver section of the AN/GRC-171. Figure FO-14

locked loop frequency synthesizer. The phase-locked

shows power dis- tribution of the overall radio set. Power

loop receives binary- coded-decimal (bcd) frequency

distribution will be discussed in detail in this section.

select information from the radio control and provides

through a transmit/ receive switch either a transmit rf

4-5. OVERALL SYSTEM OPERATION.

signal (225.000 to 399.975 MHz) to the transmitter or a

receive injection signal (195.00 to 369.975 MHz) to the

4-6. Refer to figure FO-3. The radio set is capable of

receiver. Receiver-transmitter keying is provided by

transmitting or receiving either narrow-band voice audio

keying circuits that convert remote key information into

or wide-band data (including secure voice data) on 1 of

two transmitter key lines (key 1 and key 2). Power

7000 channels (25-kHz channel spacing) in the ultrahigh-

supply voltages are provided by a transformer/ rectifier,

frequency (uhf) band of 225.000 to 399.975 MHz. The

two dc-dc converters, and a voltage regulator that

radio set can be operated either locally by controls

together convert input ac power line voltage (or dc input

located on the front panel of Radio Receiver-Transmitter

voltage) into regulated power supply voltages.

RT-980/ GRC-171 (receiver-transmitter) or remotely by

controls located on Radio Set Control C-7999/GRC-171

4-8. The receiver section of the receiver-transmitter is a

(radio control).

For the purpose of this general

double-conversion receiver with the first inter- mediate

discussion, assume the system is operated remotely

frequency (if) of 30 MHz derived from mixing the

from the radio control. The radio set can be powered

incoming receive rf signal with the receive injection

from either a 120- or 240-V ac power line or from a 22-

signal. The second intermediate frequency of 10.7 MHz

to 30-V dc source or from a 24-V dc battery.

is derived from mixing the 30-MHz if signal with a 19.3-

MHz oscillator signal. The 10.7-MHz if signal is detected

4-7. The receiver-transmitter consists of a receiver

into receive audio. The receive audio is amplified,

section (lower half of figure FO-3) and a transmitter

filtered, and then fed

4-1