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Equipment
The test equipment specified on page 7 or its equivalent,
is required to properly perform the alignment procedures
which are outlined on the following pages. Use of equip-
ment which does not meet these requirements may result
in the inability to properly align the instrument.
A warm-up period of at least fifteen minutes should be
allowed for proper stabilization of equipments such as
Marker and Sweep Generators.
It is essential that the proper bias values, as specified,
are maintained during alignment to insure the proper
results.
Equipment Terminations
The alignment pads and the input lead are designed for
correct matching of the equipment to the circuits involved.
Failure to use proper matching will result in responses
which cannot be depended upon as representing the true
operation of the receiver. The pads should be constructed
as compactly as possible and all unshielded leads at the end
of the test equipment cables should be as short as possible,
preferably not in excess of one inch long. In many
instances a small ceramic capacitor, approximately lOOOPF,
connected from the oscilloscope probe to ground will
eliminate stray pick-up of unwanted signals. If used, make
sure the capacitor does not affect the shape of the response
being observed.
Signal Overload
Use of excessive signal from the Sweep Generator can cause
overloading of the receiver circuits. To determine that this
condition is not present and that the response curve is true,
turn the Sweep Generator output to zero and then gradually
increase the output until a response is obtained. Further
increase of the sweep output should not change the con-
figuration of the response except in amplitude. If the
response changes in configuration, such as flattening at the
top or dropping below the base line at the bottom, decrease
the sweep output to restore the proper configuration. The
oscilloscope gain should be run as high as possible to main-
tain a usable pattern with the peak-to-peak values specified,
thus requiring a lower output from the Sweep Generator
and less chance of overload.
Insertion of markers from the Marker Generator should
not cause distortion of the response curve. The markers
should be kept as small as possible and still remain visible.
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Troubleshooting
