TM 11-840-281-35/1
prevent this, the positive signal at the emitter of Q1404
Q1401 and Q1402 to the base of transistor Q1403.
is coupled back to the emitter of Q1403, causing the
The emitter of Q1403 (Fig. 216) is coupled to the emitter
collector of Q1403 to go positive. This positive signal is
of Q1404, causing the collector of Q1404 to swing
coupled through the closed contacts of K1402 and
positive. From the collector of Q1404, the amplified video
clipping diode CR1405 to the collector of Q1404,
is applied to the base of emitter-follower transistor
canceling the negative signal.
Q1405. The signal from the emitter of Q1405 is ac-
Diode CR1405 prevents the negative signal from the
coupled to the base of emitter-follower transistor Q1406,
collector of Q1403 from canceling the positive signal
to pre- vent the positive dc level at the emitter of Q1405
during the first portion of the ftc action.
from being applied to the base of Q1506. Diode CR1406
CLIP ADJ control R1423 balances the output at the
clamps to the base of emitter-follower transistor Q1406
collectors of Q1403 and Q1404 so the negative-going
at approximately -1.0 volt al- lowing capacitor C1409 to
excursion of Q1404 collector is clipped near the baseline
discharge rapidly, and also sets the dc output level of the
(5) When Radar Receiver-Transmitter RT-
video amplifier.
818/TPN-18 is switched to the narrow-pulse mode,
Video clipping action is provided by series-clip- ping
PULSE WIDTH SELECT relay K1401 re- moves 0.8-sec
delay line DL1402 and inserts 0.2- sec delay line
diode CR1407. When the positive video at the emitter of
Q1406 rises to within 0.7 volt of the voltage at the anode
DL1401 into the circuit providing narrow-pulse video
of diode CR1407 (set by volt- age divider resistors
delay.
R1432 and R1433), diode CR1407 shuts off. This
(6) Ftc action for narrow-pulse mode is identical
prevents any further in- crease in the video signal from
to that for wide-pulse mode. Equal amplitude into both
being applied to the base of emitter-follower transistor
sides of the differential amplifier on the narrow-pulse
Q1407.
mode is obtained by adjusting NP BAL ADJ control
Emitter-follower transistor Q1407 provides the current
R1411.
gain required to drive the video to Control-Indicator C-
2-5. Antenna Control and Data
6988/TPN-18.
Section Description
(3) When FTC switch S605 on Control-Indicator
(fig. 7-8)
C-6988/TPN-18 is placed to ON, relay K1402 is
a. General The antenna control and data section
operated. With Radar Receiver-Transmitter RT-
performs the following primary functions: provides drive
818/TPN-18 in the wide-pulse mode, the positive-going
for Azimuth Antenna AS-1292/ TPN-8 and Elevation
video at the output of emitter- follower Q1402 is applied
Antenna AS-1291/TPN-8; provides the switching and
to the base of transistor Q1403 and to 0.8 Sec delay line
control required for the antenna synchronization and
DL1402 through the contacts of wide-pulse select relay
sweep during five different modes of operation; and
K1401.
provides three output signals to the control-indicator
With the ftc function selected, Q1403 and Q1404 are
section circuits (elevation servo data, azimuth tilt data,
connected to operate as a differential amplifier. The
and azimuth and elevation angle volts).
positive-going video at the base of Q1403 swings the
These voltages are applied to the control-indicator
collector of transistor Q1404 positive.
section circuits to develop the azimuth and elevation
After being delayed 0.8 sec by delay line DL1402, the
blanking pulse for range mark blanking.
video signal is applied to the base of transistor Q1404. If
the video signal is still present at the base of transistor
(1) The antenna control and data section
Q1403 and is equal in amplitude to the delayed video at
consists of Antenna Drive TG-114/TPN-8, Antenna Drive
the base of transistor Q1404, the differential action will
TG-113/TPN-8, electronic control preamplifier, drive
cause the collector of Q1404 to fall to the same level as
motor amplifier (including circuitry of the electronic
when no video is applied to either input of the differential
control amplifier), Remote Switching Control C-
amplifier. The result is a positive- going 0.8-sec video
6989/TPN-18, two identical electronic filters, and two
signal at the collector of Q1404.
identical antenna servo actuator assemblies.
(4) The balance of input signals to the dif-
ferential amplifier is adjusted with WP BAL control
(2) Antenna AS1291/TPN-8 and Antenna AS-
R1416. When the video signal is no longer present at the
1292/TPN-8 are driven by their own respective
base of Q1403, the signal will still be applied to the base
mechanical drive systems. The elevation drive motor can
of transistor Q1404 for 0.8sec, causing Q1404 collector
be driven at two speeds. The azimuth drive motor is a
to go negative. To
conventional servo drive motor.
2-21
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