Re: Strategies to save/display low sample-rate data

[Fons Adriaensen]

On Wed, Apr 10, 2024 at 01:44:31PM -0400, 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?

No. I understood your 'not fast...' as referring to high CPU load, 
but clearly you meant that the time between updates is too long.

You can always do an FFT every N < 1024 samples, each time using
the most recent 1024 samples. If you apply a window before the FFT
then that should be done anyway. Choose N to have an update rate
that you like. 

Apart from compensating for the window (if any), this doesn't
provide any new information, you just have to wait less between
updates.

Ciao,

-- 
FA