The graphical fftsink uses the sampling rate to scale the axis and to determine the frame decimation to achieve frame rate. If the sample rate provided is off, you could get a weird frame rate (refresh rate too low or too high).

-Josh

On 04/18/2010 02:16 PM, David Barton wrote:
Hi,

In GRC I hooked up a signal source with a 100kHz sampling rate directly to a 
FFT sink. I accidentally listed the FFT sampling frequency as 200kHz. I noticed 
that it did not complain and all it did was shift the actual signal source 
frequency by a factor of 2. So my guess would be that the FFT block is not 
actually using the sampling rate parameter in the FFT calculations except to 
just scale the frequency axis. Is that accurate?

Thanks,
Dave







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