Re: [Discuss-gnuradio] Working at 20 MS/s

[Josh Blum]

On 05/01/2012 08:55 AM, frankist wrote:
> 
> Hi,
> 
> I was interested in working with detectors for OFDM 802.11b in my USRP2.
> I've read on the internet about this and it seems that there are people
> able to use sampling rates of 20 MS/s.
> 
> However, when I try to send an OFDM signal with 20 MHz of bandwidth, at
> the USRP2 receiver board the FFT plot shows the signal blinking.
> 

I think you are seeing the result of an FFT over a sample discontinuity.
This discontinuity is due to overflow, in other words, your computer is
not able to process at this rate.

http://files.ettus.com/uhd_docs/manual/html/general.html#overflow-underflow-notes
Are you seeing overflow (O's are being printed)?

Are there any warnings printed by the driver?
(Answering some of those warnings can help with performance)

Usually running an FFT display on RX data is not a big performance hit.
Any information about your PC that you can share? CPU? OS?

-Josh