Re: [Discuss-gnuradio] FFT size constraints?

[John Ackermann N8UR]

Attached is a screenshot of the error I get when trying to set the FFT 
size in the QT Frequency Sink to 16384.  It's possible, I suppose, that 
it could be the sink block, and not the FFT itself, that poses the 
limitation.

John

On 12/01/2017 12:02 PM, Müller, Marcus (CEL) wrote:
> What error does GNU Radio throw (that's the critical piece of info!)..
>
> There's no restriction of FFT sizes.
>
> Best regards,
> Marcus
>
> On Thu, 2017-11-30 at 14:28 -0500, John Ackermann N8UR wrote:
> > By convention, FFT sizes seem to be powers of 2.  And Gnu Radio
> > Companion throws an error if you try to set a size of 16384 -- but will
> > accept 16383.
> >
> > In some cases, I'd like to match FFT size to sample rate.  For example,
> > with a 100 sample/second rate, I'd like to use a 100 bin FFT to
> > (hopefully) get 1.0 frames per second.
> >
> > Is using a non-power-of-2 FFT simply less efficient, or are there other
> > concerns?
> >
> > And is there a reason why GRC sets the limit at one less than 16384?  If
> > 8192 is the max because of power-of-two requirements, it would be more
> > helpful to state the limitation as ">8192" rather than "<16384".
> >
> > Thanks,
> > John
> >
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QT_Frequency_Sink_FFT_error.png
Description: PNG image