CHAPTER 2. FUNCTIONING OF EQUIPMENT

TM 11-5821-284-34

CHAPTER 2

FUNCTIONING OF EQUIPMENT

Section I. BLOCK DIAGRAM ANALYSIS

achieved, the discriminator output is zero and adjustment

2-1.

Purpose and Use

of the series capacitor ceases.

a. The purpose and operation of the various

b. Operational Amplifier The operational

circuits in the antenna are explained in this chapter. The

amplifier amplifies the polarized Input signal from the

intercommunication, operation, and maintenance of

phase discriminator and provides a polarized output

equipment used with the antenna are covered in

signal to the servo rotation logic circuit and to the fine

applicable system manuals. Familiarity with antenna

tune circuit.

functioning, together with a knowledge of system

c. Servo Rotation Logic. The servo rotation

interconnections, will en-able rapid and effective

logic circuit detects the polarization of the input signal

troubleshooting of the antenna, individually, or as part of

from the operational amplifier and establishes the

a system. b The functional descriptions in paragraphs 2-

direction of the rotation of the servo motor. The circuit

2 through 2-16 are limited to the antenna. Discussions

provides an output signal to the servo motor sequencing

of associated equipment are included in separate system

logic circuit for direction of rotation or holding of the

and equipment manuals (app A)

servo motor. The holding signal is produced when an

RF-on voltage is received from the RF-on circuit. The

2-2.

General

servo rotation logic circuit also provides a signal to the

Paragraph 2-3 is a block diagram description of the

sequential pulsing logic circuit when the direction of

antenna. A schematic diagram analysis of the antenna

motor rotation is established.

is furnished in paragraphs 2-4 through 2-16. The

d. Fine Tune Circuit. The fine tune circuit

antenna is a blade type for transmission of FM signals in

provides a small variable series inductance for

the vhf band. Tuning of the antenna is automatically

incremental tuning of the antenna between steps in the

initiated when an external transmitter connected to the

variable series capacitor. The output of the circuit is

antenna is keyed. During tuning time, a 3- to 5-volt

controlled by the input signal from the operational

square wave tuning indication is supplied by the antenna

amplifier.

for use with an external tune indicator A remote manual

e. Sequential Pulsing Logic. The sequential

tuning control is provided for tuning the antenna during

pulsing logic circuit is controlled by the input from the

radio silence conditions.

servo rotation logic circuit It provides a gating signal to

the operational amplifier, a counting signal to the servo

2-3.

Block Diagram Analysis (fig. 2-1)

motor sequencing logic, and a tuning indication signal for

a. Phase Discriminator.

Operation of the

use by an external tuning indicator

antenna coupling circuit is initiated with the application of

Servo Motor Sequencing Logic. The servo

transmitted radio frequency (rf) power in excess of 1

motor sequencing logic receives an input signal from the

watt. If the transmitted frequency is below the resonant

servo rotation logic and a pulse from the sequential

frequency of the antenna, the signal polarity developed

pulsing logic. It provides sequentially controlled output

by the phase discriminator causes the servo system to

signal to the servo motor control circuit. It also provides

drive the series variable capacitor toward increased

a signal to hold the servo motor in its last pulsed position

capacitance. If the transmitted signal is above the

when rotation signals are not applied

resonant frequency of the antenna, an error signal of

opposite polarity is developed and the capacitor is driven

to reduce capacitance. When a matched condition is

2-1