TM 11-5840-281-35/1
which scans its normal search pattern through 360
aligned to produce the scan center at 15 degrees in the
degrees. The speed of Antenna AS-1292/ TPN-8 is
60 AZ mode. In the NORM mode, a portion of the 400-
adjusted to approximately 16 rpm so that it will not be
Hz reference voltage, taken at the wiper arm of the 30
synchronous with the elevation scan. Antenna AS-
OFFSET control, is applied to the summing network as a
1291/TPN-8 scans for two consecutive looks, then skips
reference shift signal; therefore, in NORM mode, the
one look. The ppi presentation displayed on slave
scan center is at 0 degree with respect to the mount. The
Control-Indicator C-6988/TPN-18 is blanked out during
resultant summing network output is amplified by a
the elevation sector scans. Elevation scan is locked out
three-stage ac amplifier and applied to a ring de-
during the time Antenna AS-1292/TPN-8 goes through
modulator. The ring demodulator output is a dc error
its precision sector so that it cannot interrupt the azimuth
voltage whose amplitude is proportional to the peak
presentation.
amplitude of the input signal. The polarity of the error
(4) Both Antenna Drive TG-113/TPN-8 and
voltage is a function of the phase of the summed signal
Antenna Drive TG-114/TPN-8 provide a dc volt- age
with respect to the phase of a 400-Hz reference voltage
proportional to its scan angle by means of ANGLE DATA
applied across the ring demodulator. The dc error
potentiometers in the respective drive assemblies. The
voltage is filtered and applied as one input to a
angle data outputs are passed through identical
differential amplifier.
electronic filters to eliminate potentiometer noise. The
The azimuth tachometer output is applied to a second
az-el switching relay in Remote Switching Control C-
ring demodulator, filtered, and coupled to the other input
6989/ TPN-18 alternately selects the filtered outputs in
of the differential amplifier as the rate feedback
the precision modes to produce the az-el angle volts
information. The rate signal is amplified to produce a
which are applied to the circuits of the con- trol-indicator
two-ended control-current signal that is coupled through
section.
emitter followers to the electronic control amplifier.
(5) Since the scan system is designed to sat- isfy
a precision scan sequence, the precision scan will be
(7) In the 60 AZ mode, the elevation drive motor
discussed first. Elevation drive motor B501 turns
is reduced to half-speed. Antenna AS-1292/TPN-8
continuously in all precision functions. In the NORM or
control circuit configuration re- mains the same, except
35 EL modes, the crank of Antenna AS-1291/TPN-8 is
that the 10-degree el synchro output is applied to the
driven at 30 rpm through a reduction gear. Antenna AS-
electronic control preamplifier through a different
1291/ TPN-8 has one up look and one down look for
dropping resistor to provide the proper ratio with the
each revolution of the crank, or one look-per-second.
azimuth position signal. Also, the 30-degree azimuth
Two synchro units are geared to the crank at a 1:1 ratio,
reference-shift signal is removed in this mode.
one for 10-degree elevation scan, and one for 35-degree
(8) In the 35 EL mode, the elevation actuator is
elevation scan; thus, for one complete rotation of the
operated to place Antenna AS-1291/TPN-8 drive linkage
crank, the rotor of each synchro completes one full turn.
in the 35' EL position. Antenna AS-1292/TPN-8 control
One revolution of the rotor produces a 400-Hz output
circuit configuration is the same as in the NORM mode,
voltage signal that is amplitude-modulated and phase-
except that the 35 el synchro output is utilized (instead
modulated (i.e., in-phase or 180 degrees out-of-phase
of the 10' el synchro output) as the azimuth drive signal.
with the reference).
(9) In the simultaneous mode of operation,
(6) In NORM mode, the 10-degree el synchro
Antenna AS-1292/TPN-8 is driven independently of
output is applied, through the appropriate drop- ping
Antenna AS-1291/TPN-8. When Radar Set AN/TPN-18
resistor, to the electronic control preamplifier as the
is interconnected with the associated iff equipment, an
azimuth drive signal. The 10-degree synchro output is
error voltage is supplied by a control transformer in the iff
selected by a relay in Remote Switching Control C-
pedestal, which is applied to the input of the electronic
6989/TPN-18. A similar signal is taken from the azimuth
control preamplifier. The electronic control preamplifier
synchro, which is linked to the azimuth drive motor. The
output causes Antenna AS-1292 TPN-8 to rotate in
azimuth synchro output is called the azimuth position
synchronization with the iff antenna. If the iff equipment
signal, and is applied to the electronic control pream-
is disconnected or the iff interlock circuit is opened, a
plifier where it is summed with the azimuth drive signal.
portion of the 400-Hz reference voltage from the wiper
The azimuth synchro is mechanically
arm of SEARCH
2-23
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