N9030B PXA Signal Analyzer Service Guide 159
RF Section Troubleshooting (RF/Microwave Analyzers)
Troubleshooting
A9 Input Attenuator and A10 Input Attenuator Verification
Calibrator Switch Test
On the A16 Reference assembly, disconnect semi rigid cable W3 from A16J701
and measure A16J701 with a spectrum analyzer. Expected signal is 50 MHz at
−25 dBm ± 0.5 dB. If signal level is incorrect, suspect A16 Reference assembly
is faulty, or the 50 MHz calibrator amplitude requires adjustment using the
field calibration software.
To verify calibrator switch operation, connect external signal source set to 50
MHz and −25 dBm to the RF input connector of analyzer under test. Press
Input/Output, RF Calibrator, Off. If the signal level at the attenuator output is
now correct, suspect the A9 Attenuator cal switch or a faulty control signal
from the A15 Front End Controller assembly.
Attenuator Check
Set the signal source connected to the analyzer input port to 0 dBm. On the
analyzer, press Amplitude, Attenuation, and change input attenuation to 0 dB.
The measuring spectrum analyzer connected to A10 Attenuator output port
should indicate a 0 dBm level.
Change the input attenuation on the analyzer under test to 2 dB. See the chart
below for expected measurement values at the A10 Attenuator output port.
Analyzer Under Test
Attenuator Setting (dB)
Power at A10 Output
Port
Input Attenuator Being
Tested
0 0 dBm (reference) Both set to through path
2 −2A9
4 −4A9
6 −6 A10
8 −8 A9 set to 2 dB,
A10 set to 6 dB
10 −10 A10
20 −20 A10
30 −30 A10
40 −40 A10
50 −50 A10
60 −60 A10
70 −70 A9 set to 4 dB,
A10 set to 66 dB
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