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 SB 740-91-01
Step
Setting and Instructions
Normal Indication
7
(c)
Connect the VTVM to measure DC volts
This shall occur between 50
(cont.)
at AlJ2 of the RF preamplifier. Increase
and 150 microvolts.
the output of the signal generator until
the voltage begins to rise.
If the voltage does not rise, adjust
The adjustment of the main
A3R31 on the third IF amplifier to
receiver AVC is now complete.
achieve the above results
(d)
Adjust the signal generator for 1,000
The audio level of the guard
microvolts 243.00 MHz modulated 30 per-
receiver is now set.
cent at 1,000 Hz, and with the switches
of the control box set at GD XMIT and
T/R+G position, adjust A4R20 on the
audio modulator for 100 milliwatts
across 150 ohms.
(e)
Adjust the signal generator for 1.8 to
The squelch level of the
2.2 microwatts output modulated 30 per-
guard receiver is now set.
cent at 1,000 Hz and re-peak the signal
generator to 243 MHz. Slowly turn A7R51
on the guard receiver to open the
squelch.
(f)
Adjust A3R46 on the guard receiver so
Adjustment of guard receiver
that the audio output as read on the
AVC is now complete.
audio wattmeter TS-585 D/U does not vary
more than i3 db when the signal generator
is varied from 10 to 100,000 microvolts.
8
Sensitivity Tests
With the equipment connected as shown in
The resulting receiver audio
output shall be at least 14
knobs of the control box to the extreme
milliwatts and the signal-
clockwise positions. Modulate the signal
plus-noise to noise ratio
generator 30 percent at 1,000 Hz. Adjust
shall be at least 10 db.
the signal level of the signal generator
to 4.2 microvolts output to the main
receiver or 5.0 microvolts to the guard
receiver.
If these results are not obtained, check
Reject the equipment if the
the receiver sensitivity resistor A3R34,
required test results are not
making sure it is adjusted maximum clock-
obtained.
wise, and repeat the above tests.
B-80
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