TM 11-5840-281-35/1
(n) Rotate OUTPUT ATTEN. control
cursor until cursor index mark aligns with red mark
3-34. Difference Receiver Channel Alignment
(PWR SET) on OUTPUT ATTEN. control dial.
(o) Alternately place function switch to
a. Test Equipment Required.
OFF and CW. Power meter indication should be ZERO
(1)
Oscilloscope
AN/USM-140B
SET in OFF, and 0 DBM (PWR SET) in CW. If
(oscilloscope).
necessary, readjust ZERO SET control (in OFF position)
(2) Radar Test Set AN/UPM-6 (radar test
and OUTPUT ATTEN. control and cursor (in CW
set).
position) as required.
b. Equipment Conditions and Connections.
(1) Radar Set AN/TPN-18 turned on and
NOTE
front and rear covers of Radar Receiver-Transmitter RT-
818/TPN-18 removed for access to controls.
The radar test set calibration must be checked
(2) On master Control-Indicator C-6988/
by performing steps (k) through (o) above if
TPN-18 and Pulse Generator O-1333/TPN-18, SCAN
frequency of radar test set is changed after initial
MODE switch placed to NORM, FTC and STC switches
OFF, IF GAIN EL control and EL target control fully cw.
(3) Test equipment connected as shown in
(2) On radar test set, place controls to
c. Procedure.
positions indicated below.
(a) Function switch: PULSE-EXT
(1) Calibrate radar test set for 0 dbm at 1.0-
SYNC (-).
mw power output level as follows: (a) Place POWER
(b) RF POWER SWITCH: POWER
switch 'to ON and allow 10 minutes for warmup.
OUT.
(b) Place rf power switch to POWER
(c) PULSE LENGTH: 10.
SET.
(d) PULSE DELAY: 40.
(c) Set RF TUNING control to
(3) On oscilloscope, place controls to
approximate operating frequency.
positions indicated in (a) through (j) below.
(d) Place function switch to OFF.
(a) SWEEP MODE: PRESET.
(e) Adjust ZERO SET control for
(b) TRIGGER SOURCE: EXT-AC.
ZERO SET indication on power meter.
(c) HORIZONTAL DISPLAY: X10.
(f) Place function switch to INT FM.
(d) EXTERNAL VERNIER: CAL.
(g) Rotate FM AMPLITUDE control
(e) SWEEP TIME MILLISECONDS/
fully cw (100).
CM: .1.
(h) Set ADD TO PWR. METER
(f) SWEEP TIME VERNIER: CAL.
control to 0 DB (PWR SET).
(g) Vertical Presentation: CHANNEL
(i) Rotate OUTPUT ATTEN. control
A.
fully cw.
(h) CHANNEL A AC-DC: DC.
(j) Adjust RF TRIMMER until
(i) CHANNEL A SENSITIVITY: as
indication is obtained on powr meter.
required.
(k) Place function switch to CW.
(j)
CHANNEL
A
SENSITIVITY
(l) Adjust RF TRIMMER and
VERNIER: CALIBRATED.
REFLECTOR controls for maximum indication on power
meter. Maintain power meter indication below half-scale
by adjusting OUTPUT ATTEN. control to increase
NOTE
(m) Adjust OUTPUT ATTEN. control
Elevation Antenna AS-1291/TPN-8 may be
until power meter indicates 0 dbm (PWR SET).
positioned by hand by rotating knurled end of
drive motor shaft located under cover on right
side of elevation Antenna Drive TG-114/TPN-8.
(4) Position elevation Antenna AS-1291/
TPN-8 by hand to approximate scan midrange. Maintain
this scan position while performing remainder of
difference receiver channel alignment.
3-42
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