142 Keysight NFA Series Noise Figure Analyzers Service Guide
RF Section Troubleshooting (N8973B, 74B, 75B Analyzers)
Troubleshooting
Troubleshooting
Quick Check to Verify the Low Band Signal Path
The analyzer has an internal 50 MHz amplitude reference signal that is used to
verify the low band path. Refer to Chapter 12, “Block Diagrams” for details.
Equipment needed:
Functioning Spectrum Analyzer
DVM
Cables & Connectors
Turn the analyzer on and allow it to complete its full boot up process to Noise
Figure Analyzer mode. Use the internal 50 MHz, −25 dBm calibrator signal as a
reference for troubleshooting by pressing MODE/MEAS, Spectrum Analyzer,
OK, Mode Preset, Input/Output, RF Calibrator, 50 MHz on the analyzer. Now
press FREQ, 50 MHz, Span, 1 MHz, Peak Search. The 50 MHz reference signal
should measure 50 MHz @ −25 dBm ± 2 dB on the analyzer display. If the
power level is within tolerance, the low band path is functioning correctly at
50 MHz. To verify the high band path go to “Quick Check to Verify High Band
RF Path #1” on page 169.
If the power level is not within tolerance, press FREQ, Zero Span, AMPTD,
Attenuation, Mech Atten, 10 dB.
IMPORTANT Turn off auto align by pressing System, Alignments, Auto Align, Auto Align,
Off.
To perform the following checks, it will be necessary to remove the outer
cover and the top brace. See Chapter 15 for removal procedures.
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