- Hi Wolf,I am interested in using SL for this function. A 20dB reduction in Noise Floor beckons.I have this defined as "Vector addition of the (FFT o/p) samples from 2 signal paths,with subsequent Averaging". Correlated signals/noise have the same phase, so theirmagnitudes add, whilst Uncorrelated signals tend to cancel towards Zero.A clear example of this use is shown in the Rohde & Schwarz Application Note 1EF56,Figure 1, and the paragraph immediately underneath.This appears to differ from your "Correlogram", in that the output which I need is theSame as the two FFT outputs, ie Log Amplitude versus (Log) Frequency on the X axis.I wonder if this can be done from just two real signal inputs, CH1 and CH2 ??.Or are the "real-only" phase-angle values irretrievably thrown away in the process?.With separate FFT's, these are irrelevant and meaningless, but for the cross-correlation,presumably the "software local oscillator" angles need to be Common to both FFT's.Is such a feature possible in Speclab?. I'm unlikely to need it for a year or so.Graham G8PHA.