pgn0329:
Is there anything I can't catch?? I hope any opinions of yoursThanks
Yes, you make the mistake of thinking of the FFT as the only and best way to measure a tone's frequency, and
its not.
With careful interpolation from an appropriately windowed FFT you can measure peak frequency to a lot better resolution than the bin width,
However a better way to actually measure the frequency is more complicated - perhaps use FFT for initial estimate, bandpass filter out the fundamental, then refine the estimate using correlation techniques and
a model tone for comparison - basically generate a model tone at the estimated frequency and see how
fast its phase error drifts along the duration of the sample set. That allows you to refine the estimate.
A simpler approach, much easier to code, is to bandpass filter to the fundamental then estimate each
zero-crossing time by linear interpolation. Linear regression on the crossing times gives the frequency.