Adjustments Model 8901B
7.
On the Modulation Analyzer, key
in
3000
kHz
to
tune the Modulation Analyzer
to
the
signal
image. Again switch between PEAK+ and PEAK-. The difference between the
two
readings
should be less
than
1.6 kHz. If it
is
not, adjust A18R23 again
to
diminish the difference by one
half.
Now note the reading for PEAK+ (PKl+) and PEAK- (PK1-).
Press
fi
kHz.
Note the
reading for PEAK+ (PK2+)
and
PEAK- (PK2-). The instrument
is
adjusted
properly when:
I(PKl+
-
PK1-)
+
(PK2+
-
PK2-)(
<
1.6 kHz.
(Ideally, PK1+ should equal PK2-,
and
PK1- should
equal
PK2+.)
8.
Connect the FM+4 output of the AM/FM
test
source
to
the Modulation Analyzer’s INPUT.
9.
On the Modulation Analyzer, set LP FILTER
to
3
kHz. Press AUTOMATIC OPERATION.
10. Set the audio analyzer’s oscillator frequency
to
1
kHz and level
for
a display
of
50
kHz deviation
11.
On
the Modulation Analyzer, press AM. Adjust A18R19 (INC
AM
1.5
MHZ
IF)
for
a
minimum
on the Modulation Analyzer.
display (but less than 0.2%).
NOTE
The
specification for incidental AM requires that
0.5
times the residual
AM be subtracted out. The residual
FM
can be measured
by
momentarily
disconnecting the audio input
to
the AM/FM test source and noting the
displayed AM. Subtracting
0.5
times the displayed AM from the AM
measurement in step
11
gives the actual incidental AM.
5-20 Adjustment 12
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