Model
8901B
Adjustments
Adjustment
20
POWER
METER
0
Service
Sheet
1
Description
The frequency of the 220 Hz multivibrator
is
adjusted
for a maximum power reading of a nominal
input signal. This occurs when the phase shift through the ac amplifier chain of the power meter
is
zero.
Two
linearity adjustments are then made on the two highest power ranges using
a
power meter
range calibrator.
Equipment
Extender Cable
.............................................................
HP 08901-60179
Range Calibrator..
...............................................................
HP 11683A
Procedure
1.
Connect the power meter output of the range calibrator
to
the Modulation Analyzer’s SENSOR
2. On the range calibrator, set the function
to
calibrate, polarity
to
normal, and range
to
1
mW.
3.
On the Modulation Analyzer, press
RF
POWER. Adjust A53R40 (FREQ) for a maximum reading
4. On the Modulation Analyzer, press
S
(Shift) AUDIO FREQ. Set AUDIO INPUT
to
read external.
5.
On the Modulation Analyzer, connect the MODULATION OUTPUT/AUDIO INPUT
to
A53TP4
6. Remove the cable from A53TP4.
7. On the range Calibrator, set the function
to
standby.
8.
On the Modulation Analyzer, press
RF
POWER. Press ZERO and wait for the instrument
to
zero.
9. On the range calibrator, set the function
to
calibrate.
input.
on the Modulation Analyzer’s display (approximately
1
mW).
(MLTVIB).
The Modulation Analyzer’s display should read between 204 and 236 Hz.
10.
On the Modulation Analyzer, press CALIBFMIX then press the blue key then press SAVE CAL
(again, the CALIBRATE key). This normalizes the power reading
to
1
mW. (The CALIBRATE
key light should be on.)
11.
On the Modulation Analyzer, key in 10.4 SPCL
to
set the power meter
to
range 4.
12. Set the range calibrator range
to
10 mW. The Modulation Analyzer’s display should read between
9.99 and 10.01 mW.
If
it does not, perform the following
steps.
a.
Switch the Modulation Analyzer
off
and extend the A53 RF Power Assembly.
b. Connect the extendercable
to
the RF Power Assembly. Connect the range calibrator
to
the
c. Switch the Modulation Analyzer back on. Repeat
steps
7
to
12.
d. Adjust A53R13 (RNG 4) for a Modulation Analyzer display of 10.00 mW.
sensor connector on the extender cable.
13.
On
the Modulation Analyzer, key in 10.5 SPCL
to
set the power meter
to
range
5.
Adjustment
20
5-33
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