The loopback <https://www.ettus.com/product/details/LPBK-KIT> kit is a 30dB attenuator and an SMA cable sold by Ettus Research.
On Thu, Sep 19, 2013 at 8:40 AM, Ian Buckley <i...@ionconcepts.com> wrote: > Can you describe for us what the "loopback kit" comprises? Theres > hopefully significant attenuation in the signal path. > > On Sep 19, 2013, at 7:53 AM, "Marcus D. Leech" <mle...@ripnet.com> wrote: > > On 09/19/2013 10:45 AM, Isdren Gineer wrote: > > I am using N210 USRP's with WBX daughtercards connected with a loopback > kit implementing a 8-PSK waveform. When I start transmitting, I get a clean > constellation. After a short time however (~5 sec) it appears that the > receiver temporarily loses phase lock. The eight point constellation > degrades such that many points appear in a circle with the same radius as > the points. The FFT of the signal shows that the noise floor temporarily > rises. It's as if the amplifier begins to clip or some other non-linear > process is occurring. After such a 'burst' the constellation appears clean > again until another burst occurs. Has anybody else observed this behavior? > Any ideas to what could be the underlying issue? > > I am using an multiplier to set the signal amplitude to 0.3 and have the > gains of the USRP's set to around 7dB. If I use a higher amplitude or > greater gains, performance degrades quickly. Are there any rules of thumb > for these settings? Why does the performance degrade with increased values? > > > _______________________________________________ > Discuss-gnuradio mailing > listDiscuss-gnuradio@gnu.orghttps://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > You're either getting ADC clipping, or your receiver is entering a > non-linear operating region where harmonic distortion starts to happen. > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > >
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