TM 11-5840-281-35/1
(j) Adjust RF TRIMMER until
(8) On stc unit, rotate SUM STC GAIN
indication is obtained on power meter.
control R3913 and DIFF STC GAIN control R3914 fully
(k) Place function switch to CW.
cw. Rotate STC SLOPE control R3911 fully ccw.
(I) Adjust RF TRIMMER and
(9) On radar test set, place controls to
REFLEC- TOR controls for maximum indication power
positions indicated in (a) through (e) below.
meter. Maintain power meter indication below half-scale
(a) Function switch: PULSE-EXT
by adjusting OUTPUT ATTEN. control ccw.
SYNC.
(m) Adjust OUTPUT ATTEN. control
(b) Rf power switch: POWER OUT.
until power meter indicates 0 dbm (PWR SET).
(c) PULSE LENGTH: 10 (u sec).
(n) Rotate OUTPUT ATTEN. control
(d) PULSE DELAY: 20.
cursor until cursor index mark aligns with red mark
(e) OUTPUT ATTEN.: 30.
(PWR SET) on OUTPUT ATTEN. control dial.
(10) On radar test set, adjust RF TUNING
(o) Alternately place function switch to
control for maximum pulse on oscilloscope. While
OFF and CW. Power meter indication should be ZERO
adjusting RF TUNING control for maximum pulse on
SET in OFF, and 0 DBM (PWR SET) in CW. If
oscilloscope, maintain pulse below limiting level by
necessary, readjust ZERO SET control (in OFF position)
adjusting OUTPUT ATTEN. control on radar test set and
and OUTPUT ATTEN. control and cursor in (CW
CHANNEL A SENSITIVITY control on oscilloscope.
position) as required.
(11) Check radar test set calibration as in
(p) Rotate OUTPUT ATTEN. control
para c(5) (k) through (5) (o) above.
fully cw.
(12) On oscilloscope, adjust CHANNEL A
VERTICAL POSITION and CHANNEL B VERTICAL
POSITION controls to superimpose both sweeps on
NOTE
center horizontal grid line.
(13) On oscilloscope, adjust HORIZONTAL
The radar test set calibration must be checked by
POSITION control so that start of sweeps is at far left
performing (k) through (o), above, if frequency of
vertical grid line.
(Since sweeps are triggered by
radar test set is changed after initial calibration.
pretrigger, far left vertical grid line now represents first
pretrigger time, and each centimeter on horizontal grid
(6) On oscilloscope, place controls to
line is 100 microseconds.)
positions indicated in (a) through (o) below.
(14) Observe that second pretrigger
(a) POWER: ON.
appears at 833 +40 microseconds on oscilloscope
(b) SWEEP MODE: PRESET.
display.
Adjust CHANNEL B SENSITIVITY and
(c) TRIGGER SOURCE: EXT AC.
CHANNEL B SENSITIVITY VERNIER so that pretrigger
(d) HORIZONTAL DISPLAY: X1.
amplitude is approximately 1.0 cm.
(e) EXTERNAL VERNIER: CAL.
(15) On stc unit, adjust GATE WIDTH
(f) SWEEP TIME MILLISECONDS/
control R3905 until receiver noise displayed on
CM: .1 (g) SWEEP TIME VERNIER: CAL.
oscilloscope is gated off 700 microseconds after
(h)
Vertical
Presentation:
pretrigger time (133 microseconds before next
ALTERNATE.
pretrigger).
(i) CHANNEL A POLARITY: +UP.
(16) On radar test set, set PULSE LENGTH
(j) CHANNEL A AC-DC: DC.
control to 1.
(k) CHANNEL A SENSITIVITY: As
(17) Adjust PULSE DELAY control until
required.
pulse appears on oscilloscope 120 microseconds after
(l) CHANNEL A SENSITIVITY VER-
first pretrigger time (120 microseconds after start of
NIER: As required.
oscilloscope sweep).
(m) CHANNEL B POLARITY: -UP.
(18) On radar test set, adjust OUTPUT
(n) CHANNEL B AC-DC: AC.
ATTEN. control until pulse amplitude is at receiver noise
(o) CHANNEL B SENSITIVITY
level on oscilloscope. Note OUTPUT ATTEN. control
(VOLTS/CM) :5.
dial
setting.
(7) On master Control-Indicator C-
6988/ TPN-18, place STC switch to ON.
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