g. Servo Motor Control Circuit. The servo

power is applied to the antenna.

k. Manual Override Logic. The manual over-

motor control circuit receives inputs from the servo motor

ride logic is provided to enable tuning of the antenna

sequencing logic and provides a ground for the +28-volt

without applying transmitted RF power.

dc power source used to drive the servo motor.

h. Servo Motor. The servo motor turns in 15-

l.

Homing Logic. The homing logic provides a

degree steps and adjusts the series variable capacitor to

signal to return the series variable capacitor to minimum

tune the antenna circuit to resonance near the

capacitance after it has reached maximum capacitance.

transmitted frequency.

m. Tuning Indicator Drive. The tuning indicator

i.

Antenna Circuit. The antenna circuit is

drive circuit receives an input signal from the sequential

pulsing logic and amplifies it to a 3- to 5-volt square-

tuned to resonance by the series variable capacitor and

wave output for use in an external tuning indicator.

by a small series variable inductance provided by the fine

n. Voltage Divider. The voltage divider circuit

tune circuit.

j.

Transmit/Receive

Logic.

The

converts the +28-volt dc input to proper input voltages for

the circuits of the antenna.

transmit/receive logic (RF-on) circuit inhibits the servo

rotation logic against tuning to erroneous signals. The

RF on circuit enables the tuning circuits when transmitter

In the detailed theory of operation discussion, the term logic "1" means a positive potential (approximately

+3.5 volts dc) and the term logic "0" means a near ground potential (approximately +0.2-volt dc). Refer to

the schematic diagrams, figures 5-6, 5-7, for overall circuit discussion and to figures 2-2 through 2-9 for

simplified diagrams of the individual circuits.

addition of the induced voltage (e2) and the sampled

voltage (e6) in circuit number 1 creates a result-ant

(figs. 2-2, 2-3)

voltage (e4). The vector addition of the induced voltage

The phase discriminator develops a dc error signal that

(e6) and the sampled voltage (e6) in circuit number 2

is proportional to the phase shift between the RF line

creates a resultant voltage (e4). The algebraic sum of

current.

the two resultants, (e4 and e5), is the error signal output.

a. The impedance presented to the RF signal

When the impedance is restrictive, the magnitude of the

by the antenna is either resistive, capacitate, or

resultant voltage (e4) is equal to the resultant voltage

inductive, depending on the signal frequency and its

(e5). The voltages are of opposite polarity and cancel

relation to the resonant frequency of the antenna**. **When

each other so the error signal is zero. When the

the RF signal frequency is below the resonant frequency

impedance is capacitive, the resultant voltage (e4)

current (iL) leads line voltage (eL) and the error signal

increases in magnitude. The algebraic sum of (e4) and

developed is positive. When the RF signal frequency is

(e5) causes a positive error signal output. When the

above the resonant frequency of the antenna the

impedance is inductive, the resultant voltage (e4)

(eL) and the error signal developed is negative. When

decreases in magnitude. The algebraic sum of (e4) and

the RF signal frequency is the same as the resonant

(e5) causes a negative error signal output.

frequency of the antenna the impedance is resistive.

Line current (iL) is in phase with line voltage (eL) and

CR1 and filtered by FL1. Resultant voltage (e5) is

there is no error signal developed.

rectified by diode CR2 and filtered by FL5.

The

b. The phase discriminator is divided into two

rectification and algebraic sums of the resultant voltages

circuits. Circuit number 1 consists of points B, C, E, and

create a dc error signal output proportional to the phase

F. Circuit number 2 consists of points A, D, E, and F.

shift between RF voltage and RF current.

The line voltage (eL) is sampled, with no phase shift,

through the capacitance between the windings of coil L3

and the transmission line. The voltage induced in L3 is

90 degrees out-of-phase with line current (iL). The vector