On Apr 10, 2024, at 11:28 AM, Daniel Estévez <daniel@destevez.net> wrote:
On 10/04/2024 19:44, John Ackermann N8UR wrote:
On 4/10/24 11:29, Fons Adriaensen wrote:
Both the decimation and 80 size 1024 FFTs per second should be peanuts
for any modern PC...
And of course you don't need to do the FFT again for every sample,
it just generates a lot of redundant data.
I understood that if you have a 1024 bin waterfall, it takes that many samples
to fill it and output a vector. With a sample rate of 80, that means about
12.8 seconds to show one line of the waterfall. Or do I have that wrong?
(I used 80 samples/sec for simplicity. The actual rate after decimating from a
1.536 ms/s stream is 93.75.)
Hi John,
Yes, that is correct. Ultimately you're hitting the uncertainty principle for
the Fourier transform. A 1024-point FFT at 80 samples/s has a frequency
resolution of 78 mHz. You need to process at least 1 / 78 mHz = 12.8 seconds of
signal to achieve that resolution.
Best,
Daniel.
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