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Phase and Amplitude Control Board 2A2 Detailed Functional Operation
TM-11-5820-873-34 Radio Set AN/URC-92 (NSN
Regulator Board 2A3 Detailed Functional Operation

TM 11-5820-873-34
interval when C1 mm pulse exists. If this action were
a  Phase Preamp. The Phase Preamp consists of
not taken, and phase were positive when 2C1 reached
differential amplifier 2A2U1, 2A2CR1, 2A2CR2 and
minimum, C1 Home FF would be set and 2A2Q6 and
related components. A + 10 VDC reference is applied
2A2Q7 would be turned on at the same time Diode
to 2A2U1-4.
The 2A2U1-5 input is a DC level
2A2CRll is connected to the 50 (-) line and removes the
proportionate to phase angle. The 2A2U1-10 output is
drive from 2A2Q7 when the reflected power falls below
referenced at a + 10 VDC level which is the null output
the threshold If the unit is homing and the 50 ohm
level.  When phase angle goes negative, 2A2U1-10
threshold point occurs before a positive phase angle
generates a corresponding output level below +10 VDC.
occurs, the home drive will be terminated by 2A2CR11.
If  phase  angle  is  positive,  2A2U1-10  is  at  a
Variable capacitor 2C1 will overshoot and the resultant
corresponding level above +10 VDC Operational levels
positive phase angle will reset the C1 Home FF.
of 2A2U1-10 are between ground and +28 VDC.
However, the driven elements have come to rest and
b. Phase Level Changer.  Components of this
slight servo action will correct the phase error to zero
function are 2A2Q1, 2A2Q2, 2A2Q3 and associated
e. C1 Drive Inhibit.
Gate 2A2U2C, 2A2Q5,
circuitry. An input, to the Phase Level Changer, above
2A2CR8 and associated resistors make up the C1 Drive
+10 VDC controls 2A2Q1 conduction Transistor 2A2Q1
Inhibit. The C1 home signal and a C1 Home FF reset,
output, in turn, controls 2A2Q3 which establishes a drive
logic 0, causes a logic 1 at 2A2U2C-8.  The logic 1
signal to the Phase Servo Preamp positive drive. Also
triggers 2A2Q5 to short out the drive signal from the
2A2Q3 provides an output to the Phase Positive Logic
Phase Level Changer during the home cycle.  This
Generator. If the Phase Level Changer input is below +
action is necessary to prevent driving 2A2Q6 while
10 VDC, 2A2Q2 conducts to provide a drive signal to
2A2Q7 is driving during the home cycle.  Transistor
the Phase Servo Preamp negative drive.
2A2Q5 is also utilized to remove the drive from the
c  Phase Positive Logic Generator.  Transistor
phase servo during intervals when reflected power is
2A2Q4 functions as a logic level generator.  When
below threshold.  This is accomplished by the 50 (+)
triggered by the Phase Level Changer, it establishes a
signal triggers 2A2Q5 through 2A2CR8 and 2A2R21.
logic level 0. This logic 0 indicates a positive phase
f.  Phase Servo Preamp.
The Phase Servo
angle to board 2A2 flip-flop functions.
Preamp  contains  2A2CR6,  2A2CR9,  2A2CR10,
d. C1 Home Flip-Flop. The C1 Home flip-flop is
2A2CR11, 2A2Q6, 2A2Q7 and required resistors.  A
comprised of 2A2U2A-B-C, 2A2Q5, 2A2CR3, 2A2CR4,
positive phase signal triggers 2A2Q6 to supply a drive
2A2CR5 and associated components When power is
signal at 2XA2-4 A negative phase signal triggers
first applied, this FF resets and 2A2U2A-3 is at logic 0.
2A2Q7 to provide a drive signal at 2XA2-5 Transistor
A C1 home signal, logic 0 at 2XA2-6, to 2A2U2A-2 sets
2A2Q6 is cutoff, when reflected power is below
the FF. The logic 1 at 2A2U2A-3 then triggers Phase
threshold, through 2A2CR9. Similarly, 2A2Q7 is cutoff
Servo Preamp 2A2Q7 to provide a drive signal at 2XA2-
through 2A2CR10 Cutoff 2A2Q7 is also accomplished
5. The same logic 1 is used by the C1 Drive Inhibit
through 2A2CR6 at C max or through 2A2CR11 by a 50
function.  The C1 Home FF is reset (home cycle
(-) signal at 2XA210
terminated) by logic 0 on the collector of 2A2Q4 or logic
g. Amplitude Preamp. The Amplitude Preamp is
0 on the C min line. In other words, the capacitor will be
comprised  of  2A2U3,  2A2CR20,  2A2CR21  and
driven toward maximum until a positive phase angle is
associated components A + 10 VDC reference is applied
detected or until the capacitor reaches maximum
to 2A2U3-4.
The 2A2U3-5 input is a DC level
capacity A positive phase angle resets the C1 Home FF
proportionate to impedance magnitude. The 2A2U3-10
by a logic 0 at 2A2U2B-5 C max resets the FF by
output is referenced at a + 10 VDC level which is the
applying a logic 0 to 2A2U2A3 thru 2A2CR7. The C
null output level. When impedance is above 50 ohms, a
max line also shorts out the output to 2A2Q7 through
negative voltage is applied to 2A2U3-5 Conversely,
2A2CR6.  This action is required because the phase
impedance below 50 ohms means a positive input to
may still be negative when 2C1 reaches maximum
2A2U3-5.  With a positive at 2A2U3-5, the output of
capacitance and, although the C1 home function is
2A2U3-10 goes to a corresponding level above + 10
terminated the negative phase would try to drive the
VDC.  With a negative input to 2A2U3-5, 2A2U3-10
capacitor beyond the end stop. Diode 2A2CR3 shorts
provides a corresponding output below + 10 VDC.
out the positive phase drive to 2A2Q6 during the interval
Operational levels of 2A2U3-10 are between +28 VDC
of the C1 home signal. This prevents the initial turn on
and ground.
of the transmitter from generating a positive phase
angle and causing 2A2Q7 and 2A2Q6 to be turned on
h. Amplitude Level Changer. The Amplitude Level
simultaneously. Diode 2A2CR4 resets the C1 Home FF
Changer includes 2A2Q10, 2A2Q11, 2A2Q12 and
when the capacitor reaches minimum capacitance and
forces the capacitor toward maximum. Diode 2A2CR5
shorts out the positive phase drive during the time

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