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AM Delay Modulator (Option 1DA/1DB analyzers only)
AM delay itself is not tested in the analyzer since it is a function of the external detector used.
However the AM delay modulator is tested for functionality. When the modulator is on, any
CW signal is AM modulated with a 27.78 kHz sinewave. his modulation produces sidebands
on either side of the CW signal when viewed on a spectrum analyzer. his test simply looks for
the sidebands to be between 22.5 and 33 dB below the CW signal level. he test is performed
at several CW frequencies. For 75
analyzers, a minimum loss pad for proper impedance
matching is needed. As discussed previously, the spectrum analyzer and network/tuner
analyzer timebases should be connected together to avoid any frequency error.
If This Test Fails
he AM delay adjustment does
that the ribbon cable is securely attached to the AM delay modulator assembly. Otherwise,
replace the AM delay modulator assembly.
Trace Noise
race noise is measured in transmission mode using the medium bandwidth at 0 dBm output
power. his test sets up a full band sweep with averaging turned on (16 averages). It then
normalizes to this trace to eliminate frequency response errors. Averaging is then turned o
and one sweep is taken. he maximum and minimum trace values are then recorded. his test
is repeated again using the narrow bandwidth. he speci cation only applies at 0 dBm.
If This Test Fails
Almost anything within the entire analyzer system can contribute to excessive trace noise.
he most likely assemblies to fail are the A5, A4, and A3, in that order. If trace noise can
be isolated to only one input (A, B, or R), then the problem is most likely in the A5 receiver
assembly. Otherwise, suspect A4 or A3.
1-26
Performance T ests
not
signi cantly a ect this test. If this should fail, rst check
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