Hi Lou - By default, the RX DC offset is enabled. You can disable it with a quick multi_usrp call:
http://files.ettus.com/manual/classuhd_1_1usrp_1_1multi__usrp.html#a7beb49c1a04a81b3e7569db482453746 Cheers, Ben On Fri, Nov 21, 2014 at 10:08 AM, madengr <rfeng...@me.com> wrote: > Might want to post this over on the Ettus list, as I am having issue with > the > X310 and LFRX and have a few threads on there with examples of diagnosing > it. The DC compensation seems to be always on (bad since the LRFX is DC > coupled), and the digital gain setting seems broke. These may be related > to > the motherboard not ID'ing the daughter board correctly since things work > fine on the N210. The DC compensation should not be an issue for your > BasicRX, but you may want to ensure the digital gain is set to zero, or > tweak it and see if it shows glitches in the time domain. I'm wondering > now > if it's just an issue on interface B since that's also what I have my LFRX > on; I need to move it to A and try it again. > > Thanks, > Lou > > > > Daigle, Andrew - 1008 - MITLL wrote > > Hello, > > > > I am running into a small issue with the X310 USRP. My basic setup > > involves receiving from two antennas (or at this point CW tones from > > signal generators) using two basic RX daughter cards. > > > > My problem is that when I pump in a -50 dBm CW tone to channel A the FFT > > plot makes sense in that it is stable with an expected value (floor ~-117 > > dB and peak -62 dB). As the signal increases the peak increases > > accordingly (i/e for a -40 dBm CW tone I see a floor of ~-117 dB and a > > peak of -52 dB). This is consistent all the way up to -20 dBm (I didn't > > want to get too close to the -15 dBm limit written on the outside of the > > USRP). When I move this signal into channel B its FFT mirrors channel A > at > > an input of -50 dBm, but as soon the signal is increased past -45 dBm the > > noise floor starts jumping from ~117 dB to ~93 dB rapidly and the peak > > jumps and stays stable 14 dB higher (-38 dB vs -52 dB for the same -40 > > dBm). Below a -50 dBm input; however, everything is identical between the > > two channels. I was thinking maybe the decimation rate is changing on the > > second channel based on the input power (but for some reason not the > > first). The thing is I am using code loosely based on the > rx_multi_samples > > example and I don't know if there is a way to specify the decimation rate > > of each of the daughter-cards as if I was using GNU radio companion (or > > even if this is even the cause of my problem and I should be looking > > elsewhere). > > > > Any thoughts? Thanks! > > > > -Andrew > > > > > > -- > View this message in context: > http://gnuradio.4.n7.nabble.com/Inconsistant-Gain-in-X310-tp51379p51381.html > Sent from the GnuRadio mailing list archive at Nabble.com. > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >
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