Keysight NFA Series Noise Figure Analyzers Service Guide 253
Analog/Digital IF Troubleshooting
25 MHz BW IF Section
A2 Analog I.F. Troubleshooting
There are three steps to verify the A2 Analog I.F. Assembly.
— Measure the input power and frequency accuracy of the 322.5 MHz signal
(from the A13 RF Front End assembly or the A15 Front End Control
Assembly).
— Measure the output power and frequency accuracy of the 22.5 MHz signal
(to the A3 Digital I.F. Assembly)
— Measure the 300 MHz input LO signal (from the A16 Reference Assembly)
Verifying the 322.5 MHz Input Power
1. Turn the instrument off.
2. Remove instrument cover. Refer to Chapter 15, “Assembly Replacement
Procedures” in this service guide.
3. Turn on the NFA and wait for the instrument to complete the boot up
process.
4. Press System, Alignments, Auto Align, Off.
5. Press Input/Output, RF calibrator, 50 MHz.
6. Verify the 50 MHz signal is at −25 dBm on the analyzer display by pressing
MODE/MEAS, Spectrum Analyzer, OK, FREQ, 50 MHz, Span, 1 MHz, Peak
Search on the NFA. The marker readout should be 50 MHz at −25 dBm
± 3 dBm. If this reference signal is measuring incorrectly, see Chapter 4,
“RF Section Troubleshooting (N8973B, 74B, 75B Analyzers)”in this service
guide.
7. To continue verifying press FREQ, Zero Span. Verify the input attenuator
on the NFA is set to 10 dB. Look near the top of the display near the center
and verify that Atten: 10 dB is visible. If needed change the input
attenuator by pressing AMPTD, Attenuation, Mech Atten 10 dB on the
analyzer.
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