Model 8901B Operation
HP
8901B
MODULATION ANALYZER
0
0
RF
OUTPUT
SIGNAL GENERATOR
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00~0~0
SENSOR
SENSOR MODULE
00
DODO
@
0
0
0
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a
DODO
*
50
OHM
Figure
3-9.
AM
Check
Setup
FM
and Phase Modulation
(OM)
Checks
23.
Set the
signal
generator’s AM
off
and set FM
to
50
kHz peak deviation
(as
measured on
its
FM
meter) at a
1
kHz rate. Press the FM key. The Modulation Analyzer should display between
45.0
and
55.0
kHz.
24.
Adjust the signal generator’s FM peak deviation for
50
kHz as displayed by the Modulation
25.
Press the OM key. The instrument should display between
45.0
and
55.0
rad.
Analyzer.
FM
De-emphasis Check
26.
Press the FM key. Press the RATIO key. If the display
is
in
dB,
press the LOG/LIN key
to
display
5%.
The instrument should display between 99.8 and
100.2%
REL. The oscilloscope should show
a sinusoidal waveform with a peak-to-peak amplitude between
0.9
and
1.1V
and a period of
1
ms.
27.
Press the LOG/LIN key. Press the RATIO key. Press the PRE-DISPLAY key. Set the FM rate
as listed in the following table. For each setting, perform the following steps:
a. Set the FM DE-EMPHASIS
off
if
it
is
on. (Leave PRE-DISPLAY
on.)
b. Set the signal generator’s FM modulation rate
to
a value approximate
to
that listed in
c. Press the RATIO key to establish a reference of
0
dl3.
d. Press the FM DE-EMPHASIS time constant key listed in the table.
e. Adjust the modulation rate (but not the level) until the displayed modulation is
-3.0
dB.
f.
Press the
S
(Shift) key then press the AUDIO FREQ key (the AM key). The Modulation
Analyzer should display a rate within the limits listed. Also, the oscilloscope waveform should
change proportionately with the display. (Allow for a times 10 amplitude at the output
of
MODULATION OUTPUT/AUDIO INPUT when FM DE-EMPHASIS
is
set to
750
ps.)
the table.
3-51
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