C3 and C6 Control Assembly 2A5 Detailed Functional Operation

TM 11-5820-873-34

with the line current. The voltage sample (shifted 90

ohms. Three separate detectors are located on this

degrees from the line voltage) is injected into the center

board. They are the Amplitude Detector, the Reflected

tap of the current sensing transformer. The output of

Power Detector and the Phase Detector.

the transformer is detected by 2A4CR4 and 2A4CR5 to

a. Amplitude Detector. The amplitude detector

produce a DC voltage proportional to the phase error

provides a method of measuring the magnitude of the

between the voltage on the line and the current in the

impedance that exists at the input to 2T1. If this

line. The output of the phase detector is nulled (near

magnitude is greater than 50 ohms, the output from the

zero) when the line current and the line voltage are in

amplitude detector will be one polarity. If the magnitude

phase. Resistor 2A4R5 is a balance control and is

of the impedance is less than 50 ohms, the output

adjusted so the output from the phase detector is nulled

polarity will be reversed. A voltage sample is derived

when the input to 2T1 (50 12 5) is terminated with a 50

from the line by capacitive divider 2A4C1, 2A4L1 and

ohm-nonreactive load. It should be noted that the phase

2A4C2. This voltage sample is rectified by 2A4CR3 and

detector is also floated on the 10V reference. The 10V

produces a DC voltage proportional to the voltage on

reference is connected to one side of the phase detector

the line. A voltage proportional to the current in the line

and all measurements are made with respect to the 10V

is generated by transformer 2A4T1 and is rectified by

reference. A capacitive load (negative phase) will cause

diode 2A4CR2 2A4C1 is a variable capacitor and is

point A to go positive with respect to the 10V reference

adjusted so the voltage sample is exactly equal to the

The output of the phase detector is fed to a differential

current sample when the detector is terminated with 50

amplifier on 2A2. The phase detector is connected to

ohms. If the magnitude of the impedance at the input to

the phase servo amplifier so that a positive phase angle

2T1 is greater than 50 ohms, the voltage sample will be

will drive the variable capacitor toward minimum

larger than the current sample. Under these conditions,

capacity while a negative phase angle will drive the

the output voltage (measured between 2A4L6 10V REF

variable capacitor toward maximum capacity. The

and 2A4L4 output) would be negative. If the magnitude

amplitude detector is phased so that an impedance

is less than 50 ohms, the current sample is larger than

magnitude greater than 50 ohms will drive the variable

the voltage sample and the output (between 10V REF

inductor toward minimum inductance while an

and 2A4L4 output) will be positive. This output is fed to

impedance magnitude less than 50 ohms will increase

a differential amplifier located on 2A2 and generates a

the inductance.

voltage suitable for driving the servo preamplifiers. It

should be noted that the amplitude detector is floating

2-19.

C3 and C6 Control Assembly 2A5 Detailed

on 10 volts and is not referenced to ground. All

measurements for the amplitude detector must be

Functional Operation

referenced to the 10 volt reference line.

(Fig FO-32)

Board 2A5 contains two bistable relays, 2A5K1 and

2A5K2. Relay 2A5K1 controls 2C6 switching relay 2K2.

b. Reflected Power Detector.

The amplitude

Relay 2A5K controls 2C3 switching relay 2K3. The

detector portion of 2A4 also provides an output

bistable operation of 2A5K1 and 2A5K2 means, each

proportional to the reflected power on the line This is

time an energize signal is received, it will assume its

accomplished by 2A4CR1, 2A4C4, 2A4L2, and 2A4T1.

opposite state Thus, if the capacitor is in the circuit it will

The voltage sample and the current sample are added

be switched out of the circuit. Conversely, if the

in 2A4CR1 and a voltage is produced between the 10V

capacitor is out of the circuit, it will be switched into the

reference and the REF PWR output. The reflected

circuit For most antennas and frequencies, 2C3 is not

power detector compares both phase and magnitude of

needed. However, with the 2C3 switching capability,

the voltage and current samples. The REF PWR output

antenna tuning Is covered for a much wider range of

Is always one polarity, that is, it is always positive with

antennas.

respect to the 10V reference Its output will be a

minimum when the unit is correctly tuned. The reflected

2-20. Servo Motor Control 2A6 Detailed Functional

power detector is important to operation because it is

Operation

used to control the operation of nearly all functions in

(Fig. FO-35)

the unit. The reflected power output from 2A4 is fed to

Two identical servo amplifiers make up the Servo Motor

2A1 and amplified in a differential amplifier, 2A1U1.

Control One servo amp drives the phase drive motor

2M1. The other servo amp drives the inductance drive

c. Phase Detector. The phase detector observes

motor 2M2.

the phase of the voltage at the input to 2T1 and

NOTE

generates a DC voltage proportional to the phase error

Since both servo amps operate

The voltage sample for the phase detector is derived by

identically,

only

one

will

2A4C22, 2A4R6, 2A4C10, and 2A4Cll This voltage

discussed in detail.

sample is shifted in phase 90 degrees by the

differentiating action of 2A4C22 and 2A4R6. The

current sample is generated by 2A4T2 and is in phase

2-21