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Page Title: C3 and C6 Control Assembly 2A5 Detailed Functional Operation
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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
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
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
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
generates a DC voltage proportional to the phase error
Since  both  servo  amps  operate
The voltage sample for the phase detector is derived by
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

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