[USRP-users] Flat response from a signal generator

Jorge Miguel jmiggal at gmail.com
Wed Nov 10 15:25:02 EST 2010


Hi,

Nick,
That is very valuable information. Actually you where right, now I can see
"signal" on my FFT display.

I found my board very dependent on movement of the wires, touching the
system with my hands and so on.....in the end I got sort of FFT display.
(Mike, before I got a flat spectrum at -300dBm)

However basic RX with Matlab works very strange because when receiving
different frequency tones, it will translates them to base band no matter
the frequency set in the signal generator. Is this normal?

One way I manage to see a signal was modulating a tone in AM (from a signal
generator). The result is that I have my carrier at base band and the
sidebands at both sides. As long as I change the frequency of the modulating
tone I saw how sidebands move towards DC frequency (if I lower my tone
frequency) or away from DC (where the carrier is) if I increment the
frequency of the modulated tone.

As a result I guess that it is not very interesting to work with the basic
RX along with Matlab.

Am I right?

Best regards,
Jorge

On 10 November 2010 19:06, Nick Foster <nick at ettus.com> wrote:

> The BasicRX will not pass signals below 0.1MHz due to the transformers
> it uses. The LFRX is an alternative daughterboard which goes to DC.
>
> Try a signal at 1MHz and see if it shows up.
>
> --n
>
> On Wed, 2010-11-10 at 16:20 +0100, Jorge Miguel wrote:
> > Hi,
> >
> > I am using USRP2 with basic RX under matlab.
> >
> > When I connect a piece of wire to my basic RX and I run commusrp2.mdl
> > I can see noise plus a DC component in the spectrum (which I no not
> > know where it comes from). However when I connect my signal generator
> > to the basic receiver I get a perfect flat spectrum. I do not get even
> > noise.
> >
> > The signal I connect is a sine wave of 20KHz. I set an amplitude up to
> > 200mvolts since I do not want to damage anything.
> >
> > Any ideas why I cannot see my single tone in the received spectrum?
> >
> > Regards,
> > Jorge
> > _______________________________________________
> > USRP-users mailing list
> > USRP-users at lists.ettus.com
> > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
>
>
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