TM 11-5840-281-35/1
(1) Upon reception of the appropriate
terminal 1 of transformer T2203 and applied to
trigger, transistor Q2201 conducts through the primary of
multivibrator transistors Q2301 and Q2302 in the range-
transformer T2201. Voltage in-phase is coupled back to
mark oscillator circuit.
c. Sweep Generator Circuit (Fig. 7-11 and 7-
the base of transistor Q2201 (by secondary windings 3
and 6) which causes Q2201 to reach saturation quickly.
50). The sweep generator circuit input is the Al trigger
This action results in a narrow pulse with a short rise
from the trigger delay generator.
time being induced in output windings 1 and 4 of
(1) Initially, sweep-gate multivibrator
transformer T2201. Diode CR2201 short-circuits the
transistor Q4502 is cut off and transistor Q4503
reverse current created by the collapse of the magnetic
conducts. The negative Al trigger applied to the base of
field about the primary winding of transformer T2201
transistor Q4502 drives Q4502 into conduction and cuts
when transistor Q2201 turns off. With TRIG switch
off transistor Q4503 by allowing the collector of Q4503 to
S2201 in the INT position, capacitor C2203 is allowed to
go negative. This negative voltage becomes the leading
charge towards -12 volts through resistors R2203 and
edge of the sweep gate. The duration of the sweep gate
R2204. When the voltage across capacitor C2203 is
is controlled by sweep-gate shutoff circuit transistor
sufficient, transistor Q2201 conducts, produces a trigger,
Q4501. In the event a gate shutoff pulse is not
and discharges capacitor C2203. The time constant of
produced, the sweep-gate multivibrator functions as a
the circuit is such that a trigger will be produced
conventional monostable multivibrator with a duration
approximately every 833 sec, which corresponds to a
which is the function of the charge path of capacitor
C4507.
repetition rate of 1200 pps. Capacitor C2202 reacts as
(2) In the 5- and 10-mile ranges, the
low impedance when transistor Q2201 fires and
sweepgate limit line is connected to -12 volts through
decouples the spike from the power supply.
RANGE MILES switch S11(0l on the front panel of Pulse
(2) The negative pulse at windings 1 and 4
Generator O-1333/TPN-18, allowing capacitor C4507 to
of transformer T2201 is coupled through diode CR2203
charge to --12 volts through the parallel resistance of
to delay multivibrator transistors Q2202 and Q2203,
resistors R4510 and R4531. This configuration limits the
causing Q2203 to conduct. SWEEP DELAY control
maximum duration of the sweep gate to 300 sec. In the
R2209 can vary the conduction time of transistor Q2203
from 3.5 to 9.5 sec and is adjusted to start the sweep at
20and 40-mile ranges, the sweep gate limit line is
connected to -12 volts through resistor R1143, which
the transmitter pulse. The positive pulse taken at the
increases the series resistance in the capacitor C4507
collector of transistor Q2303 is differentiated by capacitor
charging path, and extends the sweep gate limit to 600
C2207 and resistor R2213.
The negative spike
sec. In the 80-mile range, the sweep-gate limit line is
corresponding to the trailing edge of the multivibrator
pulse is coupled by diode CR2204 to trigger blocking
disconnected, effectively doubling the series resistance
oscillator transistor Q2204, a conventional one-shot
in the capacitor C4507 charging path and extending the
sweep-gate limit to 1200 sec. The gate shutoff circuit
blocking oscillator. The output of transistor Q2204 is a
negative spike (Al trigger) taken at terminal 1 of
provides a means of varying the sweep gate duration
from 75 to 600 sec for use with different search ranges.
transformer T2202 and applied to sweep-gate
multivibrator transistors Q4502 and Q4503 on the sweep
The approximate gate duration for the various ranges is
generator subassembly. The operation of transistors
as follows:
Q2205, Q2206, and Q2207 is identical to transistors
Duration (sec)
Q2202, Q2203, and Q2204, except that the delay of
Range
Precision
Search
multivibrator transistors Q2205 and Q2206 is a trigger
5
75
150
pulse which is applied through transformer T2203 to
10
150
300
trigger multivibrator transistors Q2301 and Q2302 in the
20
300
600
range-mark oscillator and to the base circuit of blocking
40
575
600
oscillator transistor Q2501 in the range-mark generator
80
575
1200
to cancel the first range-mark trigger. The output of
transistor Q2207 is a negative spike (B-trigger) taken at
(3) The gate length for all search ranges,
except the 40-mile range, is more than twice the length
required for the time base sweep. This causes the time
base sweep to extend to the full diameter on the face of
the crt when the off-
2-40
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