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PNA-X Leveled Power

Question asked by andyTPE on Dec 13, 2011
Latest reply on Dec 13, 2011 by andyTPE
I have an N5242A and wanted to check what kind of leveled power I could actually get from Port 1. 

I preset the analyzer, set the start and stop frequency to my range of interest and increased the port 1 power until I got the un-leveled message.  (After preset, wide IFBW, so PNA-X sweeps like the clappers, nice and fast).

I then thought I would sanity check the output power and config'd a PMAR to actually measure the power at the test port cable.  I now get a source unleveled message, when I had none before!  I re-traced my steps and found everything was repeatable.  I discovered that it appears to be the sweep time that is influencing whether the PNA-X decides to tell me it is unleveled or not.  If I have a wide IFBW (say 50 kHz, uber-fast sweeping) I can enter a source power level of P dBm before I get the unlevel message.  Now, if I then reduce the IFBW to say 1 kHz so that sweep time increases, unlevel message occurs and I need to back off power by ~4 dB.

Whilst I can live with all of this (my IFBW's are typically in the 1-10 kHz range so I can characterize there), I am curious to understand the phenomena above.  Does sweeping so fast mean that the unleveled detect fails to respond?  Or is it something more subtle....?

FW is A.09.42.01