TM 11-6625-2575-14
(5) Tighten both setscrews.
end of the display will increase sharply
as R161 is adjusted. Readjust R161
b. High Band Alignment. Adjust R161 (fig.
slightly so that the marker spacings are
7-9) for dial misalignment of approximately 10
more equally spaced.
MHz. Check the entire range for proper align-
e. Set blanking switch S102 (fig. 7-9 ) to
RF.
ment of 50-MHz markers within 1 dial divi-
sion (10 MHz).
f. Set 1.0 MHz MARKER switch to OFF.
c. Low Band Alignment.
g. Set 50.0 MHz MARKER switch to ON.
(1) Align the HIGH BAND in b above.
h. Adjust the CENTER FREQUENCY dial to
(2) Set the CENTER FREQUENCY dial
1000 MHz. Observe the 50.0-MHZ displayed mark-
to 700 MHz.
ers, so that the 1000-MHZ marker is identified
(3) Adjust the SWEEP WIDTH vernier to
in the display. As sweep width increases, more
approximately 20 MHz.
markers are displayed.
(4) Fine-tune the dial until the 700-MHz
marker is centered in the display.
width. The 1000-MHz marker will shift to the
(5) Set the BAND switch to LOW.
right in the display. This shift is normal.
center the zero beat.
the normal setting.
(7) Check the LOW BAND at 50-MHz in-
tervals, and adjust C553 if required for align-
k. Set SWEEP WIDTH switch to NARROW.
ment within 1 dial division (10 MHz).
l. Adjust SWEEP WIDTH vernier fully clock-
7-15. Sweep Width Alignment
wise.
To align the sweep width circuit, proceed as fol-
m. Set the CENTER FREQUENCY dial to
lows:
1200 MHz.
n. Adjust R131 (fig. 7-9) as
required to
cen-
ter the 1200-MHz marker in the display.
b. Set the AN/USM-203A controls as follows:
(1) BAND SWITCH to HIGH.
o. Adjust SWEEP WIDTH vernier fully coun-
(2) CENTER FREQUENCY dial to 300
terclockwise.
MHz.
p. Adjust R167 (fig. 7-9) to
display the
1200-
(3) SWEEP WIDTH switch to WIDE.
MHz marker in the center of the display at NAR-
(4) SWEEP WIDTH vernier fully clock-
ROW sweep width.
wise.
q. Set the BAND switch to LOW, and care-
(5) ALC switch to INT.
fully adjust the center frequency dial about the
(6) RF VERNIER to 0.5-volt rms output.
300-MHz graduation (red scale) to place the 300-
(7) 1.0 MHz MARKER switch only to ON.
MHz marker in the center of the oscilloscope
(8) FIXED MARKER SIZE to midrange.
trace. Note any deviation from the 300-MHz grad-
uation when the marker is in the center of the
trace. If this deviation exceeds the equivalent
lows:
of 5 MHz, an adjustment of the fixed-frequency
(1) Vertical input de-coupled.
oscillator is indicated. If this adjustment is re-
(2) Vertical gain to 0.1 volt/cm.
quired, go to r below. If this adjustment is not
(3) Horizontal input to external.
required, go to s below.
(4) Horizontal controls to produce a cen-
tered 10-cm display.
equal spacings between the 1.0-MHZ markers
s. Set the unit under test controls as follows:
across the 10-cm horizontal display.
(1) BAND SWITCH to LOW.
NOTE
The marker spacings at the right-hand
(2) SWEEP WIDTH switch to WIDE.