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On 12/01/2017 03:33 PM, John Ackermann
N8UR wrote:
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
This is definitely a Qt FFT sink thing. I've used very-large
(500K-bins) FFTs for doing de-dispersion in the past, without any
issue.
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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