TM 11-6625-2575-14
unit under test is in obvious disagreement with
tween the unit under test RF OUT connector and
table 7-1, troubleshoot the unit
under test for de-
the RF DETECTOR IN connector.
fects (sect. III). If the unit under test appears
(2) Observe the decreased amplitude in the
questionable, proceed to the alignment procedure
display which represents the attenuated output.
in section V. If the unit under test cannot be re-
(3) The difference between the attenuated
paired satisfactorily, send it to a higher main-
amplitude and the amplitude observed in f above
tenance category.
represents a difference of 2 dB in rf output to the
detector.
7-10. Typical Test Displays
( 4 ) Remove the 2-dB attenuator, and re-
b. Connect the unit under test and the oscillo-
(5) Adjust the CENTER FREQUENCY
scope to a 115-volt, 50/60-Hz, single-phase power
between 300 MHz and 1200 MHz.
source.
that the rf output does not vary more than 2.0
c. Set the front panel POWER switches of
dB or 1.0 dB.
both the unit under test and the oscilloscope to
ON. Allow a 20-minute warmup period.
NOTE
Disregard the sharp decrease in rf out-
d. Set the front panel controls of the unit un-
put at the upper and lower cutoff points.
der test as follows.:
(1)
h. To determine the rf output voltage varia-
BAND
-----------------
HIGH.
tion in the LOW BAND (vhf), proceed as fol-
(2).
ATTENUATOR. ------------ 0 dB.
lows :
(3)
SWEEP WIDTH ------------ WIDE.
(1) Set the unit under test BAND switch
(4)
SWEEP WIDTH vernier-- Fully clock-
wise.
to 150 MHz (red scale).
(5)
(2) The display shall be typically as shown
SWEEP RATE ------------ LINE.
(6)
RF VERNIER ------- Set to 0.5 volt
(7)
rms on RF
OUTPUT
that the display or detected output does not vary
meter.
more than 1.0 dB, or 0.5 dB.
(8)
ALO ----------------- INT.
NOTE
(9)
50.0 MHz MARKER ---- ON.
Disregard the sharp decrease in rf out-
FIXED MARKER SIZE Midrange.
(10)
put at the zero-beat point, and at the
(11)
MARKER SHAPER -------Midrange.
cutoff above 300 MHz.
(12)
B L A N K I N G (main P C
i. To determine minimum detector efficiency,
board) ---------------- VIDEO.
proceed as follows.
e. Set
the display oscilloscope as follows:
(1) Set the f rent panel controls of the unit
(1)
Vertical input de-coupled.
under test as in above.
(2)
Vertical sensitivity to 0.1 volt/cm.
Horizontal input to external.
(3)
(4)
Adjust horizontal display to 10 cm
(4) The minimum amplitude shall be 0.53
width.
volt, or 75-percent detector efficiency.
(5) 0.53 volt is the product of 0.5 by 1.414
by 0.75 (the detector efficiency).
g. To determine the rf output voltage varia-
j. To determine sweep linearity, proceed as fol-
tion in the HIGH BAND (uhf), proceed as fol-
lows.
lows :
(1) Set the front panel controls of the unit
(1) Insert a standard 2-dB attenuator be-
under test as in d above.