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 SB 740-91-01
Step
Setting and Instructions
Normal Indication
9
Squelch Tests
(a)
Main receiver tests. With the equip-
The signal level shall be
ment connected as shown in figure B-20,
between 1 and 3 microvolts.
adjust the signal generator for minimum
output. Check that the squelch opens and
closes with operation of the SQ DISABLE
switch on the control box. With the SQ
DISABLE switch in the OFF position, in-
crease the output of the signal generator
to the point which just opens the squelch.
If these results cannot be obtained, ad-
Reject the equipment if this
just the signal generator output to the
adjustment cannot be made.
level which produces a 6 db signal-plus-
noise to noise ratio and adjust the re-
ceiver squelch resistor A3R50 for squelch
threshold.
(b)
Guard receiver tests. With the equipment
The signal level shall be
connected as shown in figure B-20, adjust
between 1 and 4 microvolts.
ceiver guard channel frequency (243.00
MHz). With the main receiver squelch
operative and the signal generator ad-
justed for minimum output, the receiver
audio output shall be squelched. In-
crease the signal generator output to
a point which just opens the squelch.
If these results are not obtained, adjust
Reject the equipment if this
the signal generator output to the level
adjustment cannot be made.
which produces a 6 db signal-plus-noise
to noise ratio and adjust the receiver
squelch resistor A7R51 for squelch
threshold.
(c)
AVC characteristic check. With the
The audio output shall not
vary more than 3 db from the
equipment connected as shown in fig-
ure B-20, vary the signal generator
1,000 microvolt reference
input level from 10 to 100,000 micro-
value.
volts. The same check shall be made
for the guard receiver and the same
values shall apply.
B-81
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