Hi Marcus, > Von: "Marcus D. Leech" <patchvonbr...@gmail.com> > [...] > > My question is if my approach/understanding is right. > > > > In particular I do not understand Question 4 (why does noise not reduce if > > I reduce bandwidth). > If you're varying *analog* bandwidth, rather than sampling rate, be > aware that UBX doesn't have variable analog bandwidth. It's always fixed.
I see. Great point. I just found: http://ettus.80997.x6.nabble.com/USRP-users-Which-bandwidth-does-uhd-usrp-multi-usrp-set-rx-bandwidth-set-td11897.html And it seems set_tx_bandwidth() and set_rx_bandwidth() do nothing then on the UBX. I wrote before my noise level should be -174+NF+10*log10(5e6). But based on this, it should be more correctly -174+NF+10*log10(160e6) ... is that correct? (I just receive the raw samples from the USRP via USRP Source. There is no other digital filter?) > > Furthermore, I'd be interested if Question 5 is conceptually correct. > Conceptually, I don't see any problem with it, but it very-squarely > enters "consider a spherical cow" territory. You CANNOT use a purely > arithmetic analysis, due to uncertainties. I would, in fact, > encourage you to acquire a decent broad-band, calibrated, noise source for > you lab so that you can do Y-factor analysis, if for no other reason > than to satisfy yourself that the noise equations work. The issue with the bandwidth calculation above would be one of them ;-) > I've used these on a budget-sensitive project just last year: > https://g8fek.com/precision-noise-sources.html Thanks for the pointer. I think I'll get one of these. For a proper use I would need a steep filter though, correct? (in order to have a well defined total input power Pin=-174+ENR+10*log10(FilterCuroff) dBm? ) Thanks, Lukas _______________________________________________ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
