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

The equidistant spurs do really indicate RX overloading.

Overloading lead to the amplifier being non-linear. Non-linearity leads
to intermodulation, intermodulation leads to equidistant spurs.

Please add attenuation; you don't want to damage your receiver, right?

Best regards,
Marcus

On Mon, 2018-07-16 at 21:16 -0400, Justin Shetty wrote:
> This is through a cable, but without the amplifier activated. It looks identical over the air though.
>
> On Mon, Jul 16, 2018 at 5:57 PM Marcus D. Leech <mleech@ripnet.com> wrote:
> > My guess would be that the RX is ovkerloaded. Is this via cable? If so do you have plenty of attenuation inline?
> >
> > Sent from my iPhone
> >
> > On Jul 16, 2018, at 5:29 PM, Justin Shetty <jas0504@gmail.com> 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
> > >
> > > <fft_and_constellation.PNG>
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