Figure 41. Deviation frequency compensation setup.
a. Connect the following items of equipment as
e. Adjust Signal Generator SG-71/FCC to a
shown in figure 41:
frequency of 70.7 kc. Frequency Meter FR-67/U is used
to check the accuracy of this signal.
(1) Signal Generator SG-3/U.
f. Proceed to check the deviation frequency
(2) Signal Generator SG-71/FCC.
compensation in Signal Generator SG-3/U as follows:
(3) Signal Generator TS-497A/URR.
(1) Turn the DEVIATION control clockwise
(4) Frequency Meter FR-67/U.
until the first carrier null is observed on
(5) Panoramic Indicator IP-173/U.
the panoramic indicator screen.
b. Adjust Signal Generator SG-3/U as follows:
(2) Read and note the deviation as indicated
(1) Set the MODULATION switch to EXT.
by the KILOCYCLES DEVIATION meter.
(2) Place the FREQ. RANGE-MC switch to
g. Repeat procedure given in f above; use the
the 100-200 me position.
following external modulating frequencies:
(3) Set the DEV MULT switch to X10.
(1) 30.8 kc and second null.
(4) Set the DEVIATION control fully
(2) 19.65 kc and third null.
counterclockwise.
(3) 11.4 kc and fifth null.
(5) Adjust the TUNING control until the
(4) 5.55 kc and tenth null.
FREQ. IN MEGACYCLES dial indicates
h. If any of the readings obtained vary more than 5
100.
percent from the others, adjust C49 as follows: If the
c. Adjust Signal Generator TS-497A/URR to an
reading obtained at 70.7 kc is higher than the average,
unmodulated frequency which is exactly 5 mc above or
decrease C49; if the reading is lower, increase C49.
below the frequency of Signal Generator SG-3/U.
i. Repeat the procedure given in b through h
d. Adjust Panoramic Indicator IP-173/U and Signal
above with Signal Generator SG-3/U tuned to 200 mc.
Generator TS-497A/URR until a carrier pip is observed
at the center of the indicator screen.
Section IV. FINAL TESTING
89. Test Equipment Required for Final Testing
88. General
The instruments needed for testing the signal generator
This section is a guide to aid in determining the quality
are listed in paragraph 55.
of a repaired Signal Generator AN/URM70.
The
minimum test requirements, outlined in paragraphs 89
90. Test Conditions
through 94, may be checked by maintenance personnel
a. A 1/2- to 1-hour warmup period should be
with adequate test equipment and the necessary skills.
allowed before final testing is begun.
Repaired equipment must meet these requirements for
satisfactory operation.
b. Line voltage to the test setup must be 115 volts,
50 to 60 cycles.
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