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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