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Adjustments
Model 8902A
Adjustment 14-AM
Calibrator
Reference
Service Sheet 30.
Description
The Measuring Receiver is set to read YoAM as computed from internal measurements. The AM
depth is adjusted for 33.33%. The AM is then demodulated and the symmetry is adjusted as the
signal is measured with the peak+ and peak- detectors.
NOTE
This calibralion adjirstmtwl is not critical. Built-in saj2girards minimize the
possihilily
of
tw-ont'oiis calihration.
I f
conditions exisl thal arc oirf of calihra-
tion. the Mcasimhg Rtwivcr disploys an error mixsage.
Procedure
1. Connect CALIBRATION AM/FM OUTPUT
to INPUT. (The CALIBRATION AM/FM OUT-
PUT can be connected either to a sensor module or directly to the Measuring Receiver's IN-
PUT.)
2. Key in 13.0
SPCL.
This sets the instrument to display the AM computed from internal mea-
surements.
3. Adjust
A50R45
("A"
LVL) for a display of 33.330 to 33.336%.
4.
Key in
49.5
SPCL. This Connects the internal voltmeter to measure the output level from the
AM calibrator. The display should read between
1.8
and 2.2.
5.
Key in 13.2 SPCL then 5.1 SPCL. This sets the instrument t o display the demodulated AM
from the calibrator and sets the peak detector time constant to slow.
6. Alternately set the DETECTOR to PEAK+ and PEAK- and note the display for each setting.
Adjust A50R39
(SYMM)
until the readings are the same for both detectors within -f0.0159'0.
I II
II
.
I
5-24
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