TM 11-5840-281-35/1
transistors Q2402 and Q2403 are connected as a
during Antenna AS-1292/TPN-8 scan except that
differential amplifier. Since the base of transistor Q2403
emitter-follower transistor Q2401 input is switched to the
is connected to ground, the outputs at the collectors of
elevation angle data line by means of AZ-EL
amplifier transistors Q2402 and Q2403 will be of equal
SWITCHING relay K1104. Also, the variable bias input
voltage, but opposite polarity with respect to ground. As
to transistor Q2404 is switched to AZ WIDTH control
an example, assume the voltage at the base of transistor
R2437.
(6) During search operation, a ground is connected to
Q2402 is -5 volts rising toward +5 volts. The voltage
the ppi disable line through relay K1102 The ground
appearing at the collector of transistor Q2402 will be +5
keeps transistor Q2406 cut off and disconnects the
volts going toward -5 volts, while the voltage at the
transistor Q2404 and Q2405 switching circuit from the
collector of transistor Q2403 will be -5 volts rising toward
remaining circuitry. The azimuth unblanking line is
+5 volts.
connected to switch S1001 operated by the 30-degree
(3) At the start of the scan, using the same
cam in Antenna AS-1292/TPN-8 assembly. When the
representative voltage, the base of transistor Q2404 will
antenna passes through the 30-degree approach sector,
be positive, causing Q2404 to conduct; the base of
switch S1001 is actuated and a ground is placed on the
transistor Q2405 will be negative and Q2405 will be cut
azimuth unblanking line. The ground causes transistor
off. As long as either transistor Q2404 or transistor
Q2407 to conduct which, in turn, cuts off transistor
Q2405 conducts, the base of transistor Q2406 will be
Q2408, blanking the range marks.
allowed to go negative and Q2406 will be cut off. When
transistor Q2406 is cut off, the base of transistor Q2407
will be positive, which will keep Q2407 cut off. With
2-8.
Sweep Generating Circuit Description
transistor Q2407 cut off, the base of transistor Q2408 will
(fig. 7-11)
be negative and Q2408 will conduct heavily The
conduction of transistor Q2408 clamps the range mark
a. General. The sweep generating circuits
blanking line to ground; consequently, the range marks
function as part of the control-indicator section to
will not be blanked.
produce a sawtooth voltage for the rotating deflection
(4) As Antenna AS-1291/TPN-8 scans, the
coil, which produces the time-base sweep for both
voltage at the base of transistors Q2404 and Q2405
search and precision operation. The sweep generating
goes towards zero from opposite references. If the
circuits receive either the system pretrigger from the
same bias were applied to both Q2404 and Q2405
transmitter section or the delayed 1200pps or 400-pps
transistors, the equal and opposite voltage applied would
trigger from the iff equipment, and produce output
bring Q2405 into conduction at the same time Q2404
signals consisting of a sawtooth sweep voltage and a
cuts off, and no blanking pulse would develop. This
sweep gate. The sawtooth sweep voltage is routed to
situation is corrected by providing a variable bias to
Control-Indicator C-6988/TPN-18 as the deflection
transistor Q2404 from the center tap of EL WIDTH
voltage for the indicator sweep. The sweep gate is sent
control R2438. By increasing the back bias on transistor
to the indicator circuits and becomes the intensity gate
Q2404 with respect to transistor Q2405, Q2404 will cut
for the indicator. The sweep generating circuits are
off before Q2405 begins to conduct. During the period
located on the trigger delay generator, sweep generator,
both Q2404 and Q2405 transistors are cut off, the base
and the rotating coil amplifier subassemblies.
of transistor Q2406 is positive and Q2406 conducts. The
b. Trigger Delay Generator Circuit (fig. 7-11
conduction of transistor Q2406 causes transistor Q2407
and 7-51). The input to the trigger delay generator circuit
to conduct, which cuts off transistor Q2408. When
is the negative pretrigger pulse from the transmitter
transistor Q2408 is cut off, a negative voltage appears
section, or the delayed 1200-pps radar trigger from the iff
on the range-mark blanking line, thus blanking the range
equipment through R ANGE MILES switch S1101. In iff
marks.
AZ TILT POS control R2431 provides a
operation, position 5 of the switch selects the 400-pps
calibrating voltage to the azimuth tilt data voltage, and is
trigger from the iff equipment. The pretrigger is applied
adjusted to make the blanking pulse occur when the
to the base of blocking oscillator transistor Q2201 on the
elevation scan angle is the same as the azimuth tilt
trigger delay generator subassembly (para 2-6a(2))
angle.
The az-el blanking pulse generator works identically
2-39
Previous Page
