Audio FFT Extension - suggestion for timing adjustment about beagle_sdr_gps HOT 4 OPEN

Yup, like that idea. Another one I had was a slider that allows fine-tuning of the interval by re-summing the FFT samples when the interval is changed. So you would click as you describe to establish the rough cycle time, integrate for a few minutes, then fine-tune until those few minutes of summing line up. You could even have a mode where the individual FFTs are shown separately as an aid to fine-tuning in the proper direction to get the alignment correct.

For a strong enough signal you could even consider implementing an automatic fine-tune that attempts to detect the leading edge.

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One downside of this scheme is that changing the characteristics of the FFT isn't really possible since the FFT is being run at a fixed audio rate and size for the benefit of the FIR filter. The benefit is that you get it computationally for free. You've probably noticed that for fast integration times (e.g. one second) line doubling of the FFT output is used to fill the vertical height of the display window. Not exactly optimal.

Not to say you couldn't write another extension that did a separate, arbitrary FFT on the audio stream with any parameters you wished.

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Sounds good.

There's another interesting visual method of correlating weak repetitive signals such as NDB's which is incorporated into this software (21 day free trial). http://www.coaa.co.uk/ndbfinder.htm

Regards,

Martin - G8JNJ

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Yes, I've seen that software. Very impressive. Could have used that back in the 1980s when I did most of my serious NDB listening, lol.

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