will cause serious errors in output
d. Set the MODULATION selector to 1000~1600 ~
voltage measurements.
Properly
or 20KC as desired.
designed constant-impedance pads,
e. Set the DEV MULT switch and the DEVIATION
matching networks, and fittings should
control to obtain the desired degree of frequency
be used wherever possible.
deviation, as indicated on tile DEVIATION meter. Read
the colored meter scale that corresponds to the indicator
19. Adjustments for Unmodulated Output (Cw)
light color. In the 50-100 mc position, read the 0-15
a. Determine the necessary test frequency.
(green) meter scale. For the 100-200 mc position, read
b. Turn the POWER switch to ON, and allow time
the 0-30 (amber) scale. For the 200-400 me position,
for warm up.
rend the 0-60 (blue) scale.
c. Turn the FREQ.
RANGE-MC switch to the
desired frequency range.
21. Adjustments for Externally Modulated Output
d. Set the MODULATION selector to OFF.
a. External modulation is required when the
e. Adjust the TUNING control for the desired
internal modulation frequencies of the signal generator
output frequency (indicated on the FREQ.
IN
are not sufficient for particular test applications. The
MEGACYCLES dial).
required external modulation source is an audio
oscillator that produces the desired frequency within the
f. Connect the R. F. OUTPUT connector to the
range of 250 to 70,000 cps and an output amplitude of
unit under test.
at least 0 dbm into 600 ohms or 774 millivolts.
g. Rotate the OUTPUT control to obtain a center
scale reading (SET TO LINE) indication on the OUTPUT
meter. (On the 200-400 mc range, set the trimmer for a
those given in paragraph 19, except that the
maximum output.)
MODULATION selector will be placed in the EXT
h. Set the movable index marker on the OUTPUT
position.
Connections are made from the external
control to the 100K microvolts mark.
(The OUTPUT
audio oscillator to the signal generator EXT.
MOD.
control dial then is read directly in dbm or microvolts.)
binding posts.
i. Set the OUTPUT control to the desired signal
22.
Stopping Procedure
output strength.
To stop operation of the signal generator, place
the POWER switch in the OFF position.
If the
20.
Adjustments for Internally Modulated Output
generator is to be idle for only a short period, it is
a. Determine the necessary test frequency.
preferable to place the POWER switch in the STANDBY
position. This keeps the tube filaments warm until the
frequency deviation desired.
generator is needed.
through i.
Section III.
OPERATION UNDER UNUSUAL CONDITIONS
23. General
24. Operations in Arctic Climates
The operation of Signal Generator AN/URM70
Subzero temperature, and climatic conditions
may be difficult in regions where extreme cold, heat,
associated with cold weather, affect the efficient
humidity and moisture, sand conditions, etc., prevail.
operation of test equipment.
Instructions and
Although every precaution is taken in the design of the
precautions for operation under such adverse conditions
equipment to maintain its technical characteristics over
follow.
a wide temperature and humidity range, adverse
a. Handle the generator carefully.
conditions may cause large errors in measurements,
b. Keep the equipment warm and dry; if necessary,
unless additional precautions are taken.
keep the signal generator in its transit case. Place the
POWER switch in the STANDBY position to aid in
effects of these unusual climatic conditions.
drying the equipment. When
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