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
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
f.
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
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
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