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 low clipping (or 70 percent of clip-
ping).
(b) Same as (a) above. When the signal in-
The wattmeter shall read 100
put level on the audio oscillator is ad-
milliwatts.
justed to 3 db below clipping.
If the wattmeter does not read 100 milli-
The sidetone output should be
watts, adjust R42 (located on the audio
indicated as not less than 14
module until 100 milliwatts is obtained
milliwatts at 30 percent
modulation.
5
Modulation Tests
For Receiver-Transmitter RT-742/ARC-51BX
use procedure (a); for Receiver-Transmitter
RT-742B/ARC-51BX, use procedure (b).
(a) Refer to figure B-19 and connect the
The voltage shall read 0.39
test equipment as shown Set the func-
volts (O DBM)
tion switch of the control unit to
T/R+G position and allow the equipment
to warm up for a least 5 minutes. Ad-
just the audio oscillator for an output
of 1000 Hz and a signal level of 2.73
volts (17 DBM) at test point "A" as read
on the VTVM. Connect the VTVM to test
point "B".
Key the transmitter by operating the CW
switch, and adjust the modulation gain
control R20, located on the modulator
and audio subassembly 1A4, to the point
at which the modulation pattern just
reaches the clipping level as viewed on
the oscilloscope OS-BC/U.
B-78
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