TM 11-6625-2575-14
h. Adjust R612, the slotted control located on
(3) SWEEP WIDTH vernier fully clock-
wise.
t. Adjust the CENTER FREQUENCY dial to
RF OUTPUT meter.
approximately 150 MHz (red scale), and place
the zero-beat notch at the extreme left of the
i. Adjust the RF VERNIER control fully
counterclockwise.
u. Alternate] y adjust low band sweep width po-
j. Monitor the rf output, and adjust potentiom-
eter R209, MIN RF LEVEL SET, a slotted, front-
panel control, for an indication of 10 dB down
beat notch and the 300-MHz marker at the ex-
from the maximum set in h above. The indi-
cated rf output shall be 0.5 mW.
k. Repeat g above with the RF VERNIER
7-16. Rf
Output Voltage Adjustment
fully clockwise.
Use the following procedures to adjust the rf
l. Adjust the CENTER FREQUENCY dial
output voltage, and the RF OUTPUT meter.
from 1200 to 300 MHz in the HIGH BAND. The
a. Set the AN/USM-203A front panel controls
power output shall be 5 mW minimum and 6.3
and S102 as follows:
mW maximum in the HIGH BAND.
(1)
BAND
----------
HIGH.
m. Set the BAND switch to LOW.
(2) ATTENUATOR ---------- 0dB.
(3) SWEEP WIDTH ---- CW.
n. Adjust the CENTER FREQUENCY dial
(4) BLANKING ---------- S102 to VIDEO.
from 500 kHz to 300 MHz (red) in the LOW
BAND. The power output shall be 5 mW mini-
(6) SWEEP RATE --------------- LINE.
(7) RF VERNIER -------- Fully clockwise.
mum and 5.6 mW maximum.
(8) ALC ----------------------------- INT.
(9) MARKERS----------- A11 OFF.
o. Repeat g through k above for an output of
5 mW minimum and 5.6 mW maximum from
b. Couple the AN/USM-203A RF OUT con-
500 kHz to 300 MHz.
nector to the AN/USM-260) power meter, using
the associated thermistor mount (477B) and
p. Repeat checks on both HIGH and LOW
the 200-ohm negative coefficient thermistor.
BAND so that l and o above are within required
limits.
NOTE
The thermistor mount uses a type-N
7-17. Marker Amplitude Adjustment
male connector for the rf input. No
adapter is required to insert this con-
nector into the BNC female connector
amplitude controls. Use the test setup in figure
of the AN/USM-203A.
7-12.
c. The RF OUTPUT meter should indicate O.
a. Eight individual marker sizes are provided.
Adjust the meter to zero, using the screw adjust-
ment if required.
markers.
d. Adjust the power meter for measurements
b. Resistor R305 adjusts the displayed ampli-
in the 0- to 10-mW range.
tude of the 1.0-MHZ harmonic marker, R311 for
the 10.0-MHZ harmonic marker, and R317 for
e. Connect the power plugs of both the AN/
the 50. 0-MHZ harmonic marker.
USM-203A and the AN/USM-260 to a 115-volt,
50/60-Hz, single-phase power source.
c. With the FIXED MARKER SIZE control
set at midrange, adjust R317 for 0.2-volt ampli-
f. Set both power switches to ON, and allow
tude of the 50. 0-MHZ marker. Adjust R311 for
a 20-minute warmup period.
0.1-volt amplitude for the 10.0-MHZ marker, and
g. Monitor the rf output, and adjust R210, the
R305 for 0.05-volt amplitude. All amplitudes are
MAX RF LEVEL SET potentiometer, a slotted
peak-to-peak values.
front-panel control, for an indication of 5 mW
on the power meter; 5 mW into a 50-ohm load
d. When using the external marker, set the
is 0.5 volt rms.
FIXED MARKER SIZE fully clockwise.