TM 11-5840-281-35/1
in the 30-degree sector of the ppi display corresponding
generator, sawtooth generator, sawtooth comparator,
to the approach sector. With the approach sector thus
cursor generator, and cursor control. The indicator
defined, the operator K102 to the input of the electronic
subsection consists of the mixer amplifier, indicator
control preamplifier. This closed loop system insures
deflection yoke, and fixed coil amplifier.
that the iff antenna and radar antenna rotate in
b. he control-indicator section performs the
synchronization. Iff interlock relay K102 will be operated
following functions:.
when the iff equipment externally selects radar operation
1) Generates the time base sawtooth
rather than iff operation. To complete the circuit for the
sweep voltage which is applied to the crt in the indicator
error voltage feedback for iff control, precision relay
subsection as the deflection voltage for the time base
K101 will be restored with the radar being in the search
indicator sweeps.
mode of operation When the radar is placed in the
(2) Provides a sweep gate to the indicator
precision mode of operation, relay K101 will be operated
circuits to unblank the crt during the sweep periods.
by the 28 volts through relay K4006 in Remote Switching
(3) Develops accurately spaced pulse trains
Control C-6989/TPN-18. The error voltage from the
which are applied to the indicator circuits as range
synchro control transformer in the iff equipment will then
marks; markers consist of range marks, touchdown
be removed from the radar antenna control circuit and
marker, and the cursor pulse.
replaced by the azimuth position feedback signal from
(4) Delivers an az-el precision expansion
Remote Switching Control C-6989/TPN-18.
signal to the indicator circuits for vertical deflection of the
(2) The rotor of the synchro control
sweep during the precision displays.
transmitter in the iff equipment is excited by the C-phase
(5) Processes the required signals to the crt
of the 120 vac power. The stator voltage is transmitted
and the deflection coils for the appropriate display on the
to control synchro B602 in Control-Indicator C-
face of the crt; signals include the composite video
6988/TPN-18 when iff relay K602 is operated. Relay
(video range marks, touchdown marker, and cursor
K602 will be operated when SCAN MODE switch S1102
pulse), intensity gate, and vertical and horizontal
on Pulse Generator O-1333/TPN-18 is placed to the IFF
deflection voltages.
position.
Connecting the iff synchro control transmitter to control
2-7.
Range-Mark Circuit Description
synchro B602 causes the ppi sweep rate to rotate in
(fig. 7-10)
synchronization with the iff antenna, regardless of the
position of Antenna AS-1292/ TPN-8.
General. The range-mark circuits function as part of the
control-indicator section to generate accurately spaced
2-6.
Control-Indicator Section Description
pulses which are used to produce range marks on the
(fig. 7-9)
crt. In search operation, the range marks indicate
distance (in nautical miles 2000 yards equals 12.36
sec) from Radar Set AN/TPN-18. In iff operation, 10-
The control-indicator section consists of five major circuit
functions: range marks; sweep operating; cursor
mile range marks are produced for the 80-mile display.
generating; cursor control; and indicator circuits.
In precision operation, the range marks are adjusted to
indicate distance from the touchdown point Means are
NOTE
also included within the range mark circuits to blank out
When Radar Set AN/TPN-18 is used
portions of the range marks and azimuth displays are
with switching capability in a landing
blanked to indicate antenna servo positions.
The
control central system, master operation
blanked area in the elevation display range marks
of either Control-Indicator C-6988/ TPN-
corresponds appearing on the crt to provide the operator
18 can be selected, with the second
with additional information. In search operation, the
display assuming slave operation
range marks are blanked is able to direct the aircraft into
position for a precision approach. In precision operation,
a. The range marks, sweep operating, cursor
sections of the range marks in both the elevation to the
generating, and cursor control subsections consist of
azimuth antenna (antenna AS-1292.'TPN-8) tilt
nine plug-in circuit cards as follows: sweep generator,
trigger delay generator, range mark oscillator, rotating
coil amplifier, az-el blanking pulse generator, range mark
2-35
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