TM 11-5840-281-35/1
b. Equipment Conditions and Connections.
(4) Measure interpulse period (time
between pretriggers) by measuring along graduated
(1) Radar Set AN/TPN-18 turned on and
horizontal gridline. Interpulse period should be 830 t40
front and rear covers of Radar Receiver-Transmitter RT-
sec. If necessary, adjust PRF ADJ control R247 on
818/TPN-18 removed for access to controls.
(2) On radar transmitter, 1/2 POWER-
radar transmitter until interpulse period is 830 Sec.
NORMAL switch S202 and NORMAL-MTI switch S201
(5) Disconnect oscilloscope.
placed to NORMAL.
(6) On radar transmitter, check magnetron
(3) On master Control-Indicator C-6988/
current indication on MAG CUR meter M201. Magnetron
TPN-18 and Pulse Generator 0-1333/TPN-18, SCAN
current should be between 20 and 26 ma.
MODE switch placed to SEARCH, SCAN switch OFF,
(7) On echo box, rotate TUNING control
TRANSMITTER switch placed through WIDE to HV ON,
until radar transmitter operating frequency is indicated on
HV ON indicator lighted, IF GAIN-AZ control fully cw, and
FREQUENCY dial.
LO TUNE control placed to midposition.
(8) Rotate METER SENSITIVITY control cw
(4) Radar transmitter operating at correct
until indication on echo box meter is between one-half
frequency.
and three-quarter full-scale deflection.
(5) Oscilloscope connected as shown in
figure 8-82.
NOTE
c. Procedure.
If unable to obtain indication on echo box meter,
(1) On master Control-Indicator C-988/
rotate METER SENSITIVITY to maximum cw
TPN-18, place ANTENNA switch to U or D as required to
and adjust MAG FREQ ADJ control on radar
tilt azimuth Antenna AS-1292/ TPN-8 to 0-degree tilt
transmitter slowly cw or ccw as required to
angle as indicated on AZ TILT meter.
obtain meter indication.
Rotate METER
(2) Position azimuth antenna by hand to-
SENSITIVITY control ccw to maintain meter
ward an area with targets at medium range (10 to 15
indication below full scale.
miles).
Maintain azimuth Antenna AS-1292/TPN-8
stationary for remainder of local oscillator alignment.
(9) Adjust MAG FREQ ADJ on radar
(3) On Radar Receiver-Transmitter RT-
transmitter for maximum indication on echo box meter,
818/TPN-18 control panel, place XTAL CUR switch to
while simultaneously rotating METER SENSITIVITY
SUM 1.
control ccw to prevent meter indication from reaching full
(4) Rotate LO TUNE control fully cw and
scale.
then ccw for maximum XTAL CUR meter indication.
(10) On echo box, check radar transmitter
(5) Adjust LO ATTEN control for 0.6-ma
frequency by rotating TUNING control cw or ccw as
indication on XTAL CUR meter.
required and then readjusting TUNING control for
(6) On oscilloscope, place controls to
maximum indication on echo box meter. Adjust MAG
positions indicated in (a) through (1) below.
FREQ ADJ control on radar transmitter until radar
(a) POWER: ON.
transmitter is operating on desired frequency.
(b) SWEEP MODE: PRESET.
(11) Disconnect echo box.
(c) TRIGGER SOURCE: EXT AC.
(d) HORIZONTAL DISPLAY: X1.
NOTE
(e) EXTERNAL VERNIER: CAL.
(f) SWEEP TIME MICROSECONDS/
Do not replace covers on Radar Receiver-
CM: 50.
Transmitter RT-818/TPN-18 until alignments and
(g) SWEEP TIME VERNIER: CAL.
adjustments are completed.
(h) Vertical Presentation: CHANNEL
A.
3-31. Local Oscillator Alignment
(fig. 342)
a. Test Equipment Required. Oscilloscope AN/
USM-140B (oscilloscope).
3-38
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