RELEASED: 10/2/2006
Page 52
COMMUNICATI0NS
HSD SERIES OPERATION AND MAINTENANCE
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5.7 Pre-Corrector Adjustment:
Use the pre-corrector circuit to adjust the transmitter output for minimum spectral re-
growth. The pre-corrector circuit is located on the 1
st
IF Board which is contained in
the Up-Converter Drawer. Use the potentiometers, R18 to adjust the slope, and
R58 to adjust the threshold of the pre-corrector circuit.
Connect a spectrum analyzer (using the proper directional coupler and attenuators)
to the transmitter’s RF output connector. Set the spectrum analyzer for the correct
frequency, and 3 MHz span at 100 kHz RBW with the averaging off. Set the
reference level of the spectrum analyzer to display the visual average of the peaks
of the digital signal. Add an additional 10dB pad to the analyzer input, and then
reset the analyzer span to 20 MHz.
Alternatively adjust the two potentiometers to establish a spectral re-growth which is
-40dB from the average of the peak digital signal at ±3 MHz from the center of the
channel.
HSD 1st IF Board P/N 50521000
R18
SLOPE
ADJUST
R58
THRESHOLD
ADJUST
