Hi Ale - Reducing this query to just the USRP list since I'm guessing if there is any issue its with that side of things. I'll reiterate Marcus' query, and augment it. The performance depends on which USRP and which version of UHD you're using. You didn't mention those. Scripts are important (thanks!), but more info is required. Cheers! - MLD On Thu, Oct 11, 2018, at 1:03 PM, Mercado, Alejandra wrote: > Dear USRP and GnuRadio folks, > > I'm not sure whom to whom I should address this question, since I > don't know if the problem arises in the GnuRadio code, the drivers, or > the actual physical USRP.> > I was attempting to run an extremely simple GRC graph (attached to > this email) where the input antenna of the USRP is grounded, the > signal is taken in with UHD: USRP Source, then the samples' > magnitudes are squared, then fed through a moving average (100,000 > points), and then the result is displayed on the screen in dB.> > As I altered the sampling rate, I observed a very strange thing: the > average for the noise readings were, by and large, smoothly increasing > with the sampling rate, except at certain frequencies (specifically, > 30*2^k, k=0,1,2,3, etc). At these specific sampling rates, the noise > level would shoot up by about 20 dB.> > I'm attaching a graph of the some of the values I got, where the big > jumps are marked by their respective sampling rates.> > Can someone explain why these jumps occur? I'm guessing that when I > adjust the samp_rate, it selects the front-end filter from a filter > bank and combines that with decimation. Maybe at certain samp_rates > (30*2^k, k=0,1,2,3,...) it's right at a threshold edge where the noise > is worse. Or maybe the problem is entirely at the other end and > GnuRadio has a bug in its assignment of samp_rate values?> > Two attachments included. Comments much appreciated. > > Thanks and regards, > Ale > > _________________________________________________ > Discuss-gnuradio mailing list > discuss-gnura...@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > Email had 2 attachments:
> * noise_level_unexpected.grc 50k (application/octet-stream) > * Capture.JPG 87k (image/jpeg)
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