Troubleshooting; Quick Check To Verify The Low Band Signal Path - Keysight N8973B Service Manual

RF Section Troubleshooting (N8976B)

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. This 50 MHz calibrator is used when the analyzer
performs many of the internal alignment routines. Therefore, the functionality
of the 50 MHz calibrator and low band path are critical to passing Align All
Now. Refer to the RF Lowband Path Block Diagram (Millimeter-Wave
Analyzers) in
the block diagram.
Equipment needed:
To perform the following checks, it will be necessary to remove the outer cover and the top
brace. See
Turn the instrument on and allow it to complete its full boot up process to
Noise Figure 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. If the power level is incorrect, select the 4.8 GHz RF Calibrator and set
the analyzer center frequency to 4.8 GHz. Since several of the same signal
path components are shared between low band and high band, determining if
the problem appears in both paths is helpful.
To verify the high band path go to
on page
206
Chapter 12
Spectrum Analyzer with frequency range to 8 GHz
Signal source with output power 0 dBm and frequency range to at least
3.6 GHz
Power splitter, 11667B or 11667C
2 each, quality SMA or 3.5 mm cables
90° SMA (m) to SMA (f) adapter
MMCX (f) to SMA (f) cable
SMA (f) to SMA (f) adapter
SMA (m) to SMA (m) adapter
3.5mm (f) to 2.4mm (m) adapters (2 required)
Chapter 15 for removal procedures.
216.
for details. Reference the instrument settings box on
"Quick Check to Verify High Band RF Path"
Keysight NFA Series Noise Figure Analyzers Service Guide