Chapter 2. FUNCTIONING OF EQUIPMENT - TM-11-5820-873-340009

TM 11-5820-873-34

CHAPTER 2

FUNCTIONING OF EQUIPMENT

Section I. GENERAL

NOTE

2-1. Introduction.

Although

ANTENNA

COUPLER

This chapter describes how the radio set operates. The

CONTROL 1A2 is housed in the radio

chapter is divided into four sections which present the

set, it functions as part of the CU-

information in a logical sequence.

2229/URC-92. Certain functioning with

meter 1A2M1 will be discussed in this

2-2. Description of Sections.

section but the remainder of ANTENNA

a. Functional Operation of Radio Receiver-

COUPLER CONTROL 1A2 functions will

Transmitter RT-1277/URC-92. Section II describes the

be covered in Section III.

functional operation of the RT-1277/URC-92.

The

section progresses from a simplified system explanation

b. Functional Operation of Antenna Coupler CU-

and block diagram to detailed circuit descriptions and

2229/URC-92.

Section III describes the functional

block diagrams.

This presentation enables easy

operation CU-2229/URC-92.

identification of circuitry common in both receive and

c. Functional Operation of Circuits. Section IV

transmit functions and that circuitry specific to either

describes the functional operation of non-conventional

receive or transmit.

circuits and certain conventional circuits.

The

conventional circuits discussed in this section are those

circuits that perform functions that may not be readily

apparent to an experienced maintenance technician.

Section II. RADIO RECEIVER-TRANSMITTER RT-1277/URC-92 FUNCTIONAL OPERATION

sidetone to be generated in receiver/exciter 1A3. The

2-3. Simplified Overall Operation (Fig. 2-1).

sidetone is coupled through speaker driver 1A1A1 to

a. Operating Frequency.

The RT-1227/URC-92

speaker 1A1LS1. The receiver/exciter also uses the

operates over a frequency range of 1.6 to 29 9999 MHz.

sidetone to modulate the signals from the synthesizer.

The operating frequency is determined by the setting of

The RF output from the receiver/exciter is amplified by

FREQ CONTROL 1A1S15 and the FREQUENCY A and

RF power amplifier 1A7. The output from the RF power

FREQUENCY B front panel switches.

amplifier is passed through filter 1A5 to ANT jack

(1) FREQ CONTROL 1A1S15 selects which

1A8J1.

group of FREQUENCY switches that control the

(2) Voice Audio from the handset is coupled into

operating frequency

receiver/exciter 1A3. The receiver/exciter uses the

(2) The setting of the selected FREQUENCY

audio to modulate the signals from the synthesizer. The

switches is decoded by decoder 1A1A2 and displayed

RF output from the receiver/exciter is amplified by RF

by LED display 1A1A3.

power amplifier 1A7. The output from the RF power

(3) Synthesizer 1A4 has three output frequencies.

amplifier is passed through filter 1A5 to ANT jack

Two of the output frequencies are fixed and the third

1A8J1.

controls the operating frequency of the RT-1277/URC-

92.

b. Receive Operation. The RF signal is received at

2-4. Receiver Functional Operation (Fig. FO-1).

ANT jack 1A8J1 and passed through filter 1A5 to

a. Overall Functional Operation. Incoming RF is

receiver/exciter 1A3. The receiver/exciter converts the

filtered by the selected bandpass filters in filter module

RF signal to audio. The audio signal is amplified by

1A5 (para 2-10). The output of the bandpass filters is a

speaker driver 1A1A1 and used to drive speaker

narrow segment of the RF spectrum that includes the

1A1LS1.

frequency selected by the FREQUENCY switches. The

c. Transmit Operation.

output from the filter module is coupled into VHF mixer

(1) CW.

Operating the CW Key causes a

1A3A1 where it is fed through a high pass filter. The

signal is then amplified and mixed with the 1st local

2-1