d. Correcting amplitude distortion.
(1) Analyze the amplitude-frequency response curve, and compare the
results with the parameters for the type of service required.
If all
amplitude variations are within requirements, make no further adjustments.
Normally, satisfactory completion of delay equalization will likewise
produce satisfactory amplitude-frequency equalization. Although amplitude-
frequency equalization takes less time to perform than delay equalization,
the technician will most likely save time by first performing delay
equalization.
(2) In the event amplitude compensation is necessary, make sure the
carrier level at each selected test frequency is uniform before proceeding
further.
Adjust the AMPLITUDE control of the equalizer sections to bring
the sections within the calculated loss limits of the parameter.
(3) A repeat adjustment of some sections may be necessary because
there may be a slight interaction of loss at adjacent frequencies.
The
circuit conditioner's work has to be most accurate in the area of minimum
permissible variation within the specified parameter.
It is in this area
that his work is more critical in providing the desired results than at
other frequencies within the band of interest.
Toward this end, he must
examine the loss variations permitted by the parameter to determine the most
critical area before he begins amplitude-frequency equalization.
(4) Recheck delay at all test frequencies, and make necessary
changes. If there is an interaction of controls that prevents any section
from reaching the required parameters on either delay or amplitude
frequency, make the final adjustment to satisfy the delay parameter. Delay
is a more difficult parameter to achieve than amplitude frequency, and the
more important of the two where data transmission is involved.
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