TM 11-5840-281-35/1
C2506 to charge after the initiating pulse is gone.
and transistor Q2510 will be conducting. The collector of
The charge time of capacitor C2506 across control
transistor Q2510 will then be at approximately 0 volt,
R2511 and resistor R2512 determines the time transistor
forward-biasing NAND gate diode CR2514.
Q2505 will remain cut off. Adjustment of 5 MILE CDN
(6) When the second negative 5-mile
ADJ control R2511 is set so transistor Q2505 again will
trigger arrives at NAND gate diode CR2514, the trigger
start conducting between the fourth and fifth range-mark
will pass and be applied to the base of blocking oscillator
trigger, giving a 5:1 countdown. Transistor Q2503
transistor Q2512, firing the blocking oscillator and
provides one more feedback path than is used in the
producing a 10-mile range mark.
conventional one-shot multivibrator to improve the speed
(7) A second negative trigger will also be
with which the changes of state take place and thereby
applied to the base of transistor Q2511 and the inverted
improve the rise and fall time of the 5mile countdown
pulse will cut off transistor Q2510, changing the state of
gate.
flip-flop transistors Q2509 and Q2510. This again puts
(4) The conduction of transistor Q2505
the collector of transistor Q2510 at -12 volts, and the
permits every fifth 1-mile range mark developed by
next negative trigger will not pass NAND gate diode
blocking oscillator transistor Q2501 to pass through
CR2514. The flip-flop thereby acts as a 2:1 countdown
NAND gate diode CR2508 and fire blocking oscillator
of the 5-mile range marks to produce 10-mile range
transistor Q2507. The output of transistor Q2507 is the
marks.
e. Az-El Blanking Pulse Generator Circuit (fig. 7-
5-mile range marks which are routed to RANGE MILES
switch S1101. Also, the 5-mile range marks replace
10 and 7-53).
The inputs to this circuit are the
every fifth 1-mile range mark through diode CR2504.
unblanking gates controlled by microswitches operated
While transistor Q2505 is cut off, transistor Q2506 is
by camshafts in azimuth Antenna Drive TG-113/TPN-8
conducting heavily, placing the emitter of Q2506 at
and elevation Antenna Drive TG-114/TPN-8.
approximately -12 volts. This negative voltage at the
(1) In the quiescent state during precision
anode of NAND gate diode CR2508 prevents the
operation, amplifier transistor Q2406 is cut off, switch
negative trigger developed across resistor R2503 from
transistor Q2407 is cut off, and switch transistor Q2408
being applied to the base of transistor Q2507. When
is conducting. The conduction of transistor Q2408
Q2505 conducts, Q2506 will approach cutoff, placing the
clamps the range-mark blanking line to ground;
emitter of Q2506 at approximately zero volt, which will
consequently, no range-mark blanking occurs.
forward-bias NAND gate diode CR2508. The negative
For the purpose of this discussion, assume the system is
trigger across resistor R2503 will then cause diode
in precision mode and elevation Antenna AS-1291/TPN-
CR2508 to conduct and every fifth trigger will appear at
8 is scanning Under these conditions, the az-el blanking
the base of transistor Q2507, causing Q2507 to fire.
pulse generator will produce a pulse when elevation
(5) A negative trigger from transistor Q2507
Antenna AS-1291/TPN-8 scan angle is the same as the
developed across resistor R2522 (coincident with the 5-
azimuth tilt angle.
The elevation angle voltage is
mile range marks) is applied to NAND gate diode
summed with the azimuth tilt data (a negative voltage
CR2514 in the countdown circuit consisting of transistors
between 1 and 25 volts) across resistors R2427 and
Q2508 through Q2511. Since transistor Q2510 is cut off,
R2428.
The voltage appearing at the junction of
its collector will be at -12 volts, which will back-bias diode
resistors R2427 and R2428 is the angle voltage working
CR2514. The negative trigger will not be allowed to pass
at the reference established by the azimuth tilt data. This
through diode CR2514. The negative trigger is also
voltage (called the azimuth angle data) is coupled
applied to inverter transistor Q2511, which inverts it and
through the energized contacts of AZ-EL SWITCHING
applies it to the bases of flip-flop transistors Q259 and
relay K1104 to the base of emitter-follower transistor
Q2510. The base of transistor Q2510 is already positive,
Q2401.
The voltage developed at the emitter of
so the trigger will have no effect upon it. The base of
transistor Q2401 is coupled through temperature-
transistor Q2509, however, is negative and the trigger
compensating diodes CR2401 and CR2402 to the base
will drive it toward cutoff, causing the flip-flop to change
of amplifier transistor Q2402. Amplifier
states.
Transistor Q2509 will be cut off
2-38
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