Section III PRINCIPLES OF OPERATION - TM-11-5820-401-34-30016

TM 11-5820-401-34-3/0967-LP-432-3060

Section Ill PRINCIPLES OF OPERATION

Subject

Para

Page

GeneraI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

Receiver Signal Path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Local Oscillator AFC/Crystal Reference System . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . .

CRS Balanced Mixer A3200 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CRS Second Mixer A3300 and Crystal Switch A2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CRS First and Second IF Amp A3400/CRS Third IF Amp and

1-14

Limiter A3500 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-18

CRS Hunt Discriminator A3600, CRS Phase Discriminator A3700, and

1-15

1-19

Reference OscillatorA2000.... ...... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-19

Antenna Tuning and Protection Module A1100............ . . . . . . . . . . . . . . . . . . . . . . .

1-20

First Rf Amplifier Module A1200.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-21

1-20

1-22

Second Rf Amplifier Module A1300. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-23

1-21

1-22

Local 0scillatorA1500.. . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

1-24

First and Second lFAmplifier A4100 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

1-25

1-23

Third, Fourth, and Fifth IF Amplified Limiter and Discriminator

1-24

A4200 GermaniumTransistor Version . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

1-26

Third IF Amplifier, Limiter and Discriminator A4200A Silicon

Transistor Version . . . . . .. . . . . . . . . . . . . . . . . . . . . .

1-25

1-27

1-28

Audio and Squelch Preamplifier A4300.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

1-25

1-26

1-29

Audio Amplification/A5000.... ..... .. . . .. .... ... .. . . . . . . . . . . . . . . . . . . . . . . . . . ..

1-27

1-30

Receiver Squelch Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-13.

GENERAL.

This section contains information covering principles of operation of the major electronic assembles

of R-442/VRC. The material is presented in functional block diagram format, with supporting text

which explains the operation of each electronic module in the radio.

Details pertaining to the operation of most individual components in each module are not discussed in

this section. lnstead, the text is intended to explain the overall effect each module has on an incoming

signal, and how the module contributes to the operation of the radio. individual circuit details can be

found in the foldouts in the back of this manual.

At the DS/GS level of maintenance, electronic components within radio modules are not replaced.

Because of this maintenance approach, this section generally does not discuss the performance of

specific circuits and components such as diodes, transistors, etc. In fact, it is not necessary to

understand how the circuits in a module operate to effectively troubleshoot or aline it. However, it is

very important to know what a module actually does in order to perform signal checks attest points for

the purpose obtesting, troubleshooting, or alining the module.

1-14.

RECEIVER SIGNAL PATH.

A system block diagram showing receiver signal flow can be found in FO-10 in the back of this manual.

Refer to the foldout while reading the text in this paragraph.

Frequency-modulated rf signals are applied to the antenna tuning and protection circuits in the A1100

module (1) of the receiver's vhf section. The A1100 module passes signals of the frequency to which

the receiver is tuned, and rejects another frequencies.

1-6