Re: [Discuss-gnuradio] USRP S-Band RX

Hm, I'd agree, with 60 dB attenuation, we should at least see reduced
intermod products. OK, you said you had a spectrum analyzer that shows
the spectrum without these spurs, so I'm trying to rule out TX
overload/clipping:
Can you use the screenshot function of that spectrum analyzer (or make
a good photograph) with at most 100 kHz resolution bandwidth and a
smaller step size on your SA?

Thanks!
Marcus Müller

On Tue, 2018-07-17 at 14:49 -0400, Justin Shetty wrote:
> I've tried the same test again with 30db and 60db of attenuation. The
> average strength is lower but the FFT still has the same profile with
> the repeated spurs. The RX overloading theory seemed promising, but
> I'm not sure what to make of the situation now that attenuation had
> little effect.
>
> On Tue, Jul 17, 2018 at 2:43 PM Justin Shetty <jas0504@gmail.com>
> wrote:
> > Looks the same as with my flowgraph (which is just the USRP source
> > going straight to the constellation and fft sinks). Also for
> > reference I'm using the SBX daughterboard.
> >
> > On Tue, Jul 17, 2018 at 1:13 PM Marcus D. Leech <mleech@ripnet.com>
> > wrote:
> > > On 07/16/2018 05:29 PM, Justin Shetty wrote:
> > > > Hi all,
> > > >
> > > > I am working with an s-band radio and am receiving its OQPSK-
> > > > modulated signal on an USRP N210. The signal I'm seeing on an
> > > > FFT and constellation plot before any processing are not as
> > > > expected though. It is very different from the example shown in
> > > > the GNU Radio tutorial 7 (random source to a constellation
> > > > modulator to a channel model). I also looked at the signal on a
> > > > spectrum analyzer and it did not show the repeated peaks I am
> > > > seeing on my FFT. Does anyone know where I might be going wrong
> > > > or what's happening?
> > > >
> > > > Justin Shetty
> > > >
> > > >
> > > What happens if you just use the "uhd_fft" utility to view this,
> > > rather than your own code?
> > >
> > >
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>
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