Chapter 10 413
Analyzer Options and Block Diagrams
Tracking Generator 8593E, 8594E, 8595E, 8596E Option 010
To check excessive residual FM
Either the tracking oscillator or the ALC circuitry could be responsible
for excessive residual FM. The residual FM should be measured on
another analyzer, such as an 8566A/B or 8568A/B, using slope detection
with the analyzer set to zero span. Proceed as follows to troubleshoot
residual FM problems.
1. Perform the Residual FM performance test for the analyzer (see the
8590 E-Series and L-Series Spectrum Analyzers User's Guide). If this
test passes, the 1st LO input and 600 MHz drive signals should be
within tolerance. If the test fails, troubleshoot the LO section.
2. Monitor A10J1 pin 5 (TUNE) with an oscilloscope. Connect the
oscilloscope probe ground lead to A7TP1. The voltage at this point
should be greater than 500 mV.
• If the voltage is less than 500 mV, perform the “Frequency
Tracking Range Check.” in the Tracking Oscillator adjustment
procedure, in Chapter 2. If this check fails, perform the
“Adjustment Procedure” which follows the “Frequency Tracking
Range Check.”
• If the noise on this tune line is greater than 10 mV, troubleshoot
the A10 Tracking Generator Control assembly.
3. Monitor the output of the tracking generator with another analyzer
(the analyzer should be in zero span). Check for high-amplitude
spurious responses from 100 kHz to at least 3 GHz. If the spurious
responses are too high in amplitude, the (broadband) ALC detector
may cause the ALC loop to oscillate, generating FM sidebands. If
any spurious responses are excessively high, refer to “If
harmonic/spurious outputs are too high.” in this section.
4. If no spurious responses are present, or if the spurious responses are
sufficiently low enough in amplitude to not cause a problem, suspect
the tracking oscillator in the A3A15 assembly.
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