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MXA N9020A - intermodulation behavior issue with narrow and wide span

Question asked by mirek on Mar 4, 2016
Latest reply on May 31, 2016 by mirek
I see an issue with the intermodulation measurement on MXA Spectrum Analyzer when you expand the span and you keep the RBW and VBW narrow.
Normal way to measure intermodulation on MXA is to set Spectrum Analyzer to narrow span (1 kHz)  with RBW and VBW to Auto (it show 9.1Hz for both RBW & VBW). Also the FFT gain will be set to low. With this setting I can get system intermod to around 110dBc.

I prepare some demo to show intermodulation performance, so I set the MXA to wide Span, however I kept the RBW and VBW at 9.1Hz
I will assume that with wide Span and narrow RBW I should get the same Intermodulation performance as narrow span. I am getting around 90dBc with 5MHz span.
It look like some IF filter is disabled in the receiver path as you expand Span. I think that it is not correct behavior. 
If you keep the RBW low and you expand the span the only penalty you should see is long sweep time, not dynamic range of intermodulation. 

I wonder if there is any way to force the same setting as you have on narrow Span to get sufficient dynamic range for Intermod?

The firmware on the unin that I run is A.13.12