Agilent Technologies 8590 Series Service Manual page 431

IS THE TEST SIGNAL AT THE PROPER LEVEL?
Comments
Test Signal Level
Preamplifier OFF
Chapter 10
First LO Distribution Amplifier (LODA) 8593E, 8594E, 8594Q, 8595E, 8596E Option 009
TREE 5: Average Power Test Problems
Problems/Reasons
The test signal comes from the
8770 arbitrary waveform
synthesizer.
If the problem appears with the
preamplifier OFF (PREAMP ON
OFF, OFF is underlined), the root
cause is likely to be a spectrum
analyzer platform path problem
or DSP problem. The DLP uses
only the 8594E spectrum analyzer
hardware and the DSP card to
execute the average power
measurement.
Analyzer Options and Block Diagrams
Diagnostic/Fix Action
View the spectrum on a spectrum
analyzer screen. It is centered at
27.6 MHz. Refer to the "Average
Channel Measurement" located in
the "Making Measurements"
chapter of the 8594Q Option 190
DVB-C QAM Analyzer User's Guide
for an example of the correct signal
shape. The bandwidth depends on
the exact test being performed, but
the signal will be of the same shape
as the example.
If the signal appears to be normal,
check the output power through a
power meter. Is the test signal at
the right power level? It should be
approximately 4 dBm − 0 (8770A
attenuator setting) − pad with the
preamplifier OFF, and 4 dBm − 50
(8770A attenuator setting) − pad
when the preamplifier is on.
Replace the DSP option board with
a "known" good board. Rerun the
test to see if it passes.
If so, save the bad board and the
matching test data for division
analysis.
If not, after swapping the DSP does
not work, perform an analyzer self
calibration. Troubleshoot as a
spectrum analyzer platform
problem if it does not pass.
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