I understand that the FFT is based on the time domain measurement so I believe my problem lies within the software. I have captured data and recently the problem I am seeing has come up. If I am in Frame 5 of 12 I see the time domain waveform and the expected spectral response. However in frame 6 I see that the data for the FFT seems to be mostly below the -125 dBu range. I have exported the frame in question and see that the spectrum has components below =125 dBu but the time domain waveform is identical to the previous frame.
I can also change frames forwards or backwards and see that at one point in time a given frame will show the expected Spectral content and at other times the same frame will show the view with the spectral content below the -125 dBu power lower limit.
This happens for the latest version of the software as well as the Beta version.