Re: [Discuss-gnuradio] Noise floor falls ~5dB when TX is started

[Marcus D. Leech]

> Hello, thanks
>
> Yes, the noise-dip is frequency sensitive. I have not been able to
> fully characterize it because at
> some frequencies it's bad and at others it's quite good, and there is
> not really a understandable pattern.
> At VHF-frequencies, it's at least quite bad before I run the script.
> I tried installing the latest git version of gnuradio to test if that
> would help - it did not.
>
> Afterwards I tried installing the UHD-drivers, and porting my scripts
> to use them. I am not that deep
> entrenched in classic drivers, even though I have been satisfied with
> them until now!! Apparently,
> using the UHD-drivers seems to solve the problem!!! Now it's working
> nicely at once when the USRP is
> powered up. Thank's a lot! What's actually the problem with the
> classic drivers, is still a mystery to me.
My suspicion is that the classic drivers *just happen* to produce some
kind of localized noise (probably
  due to the aeMB in the USRP2), and I would expect such noise to have
spectral peaks.   It's probably
  the case that the UHD firmware+fpga has a different spectral
signature.  Just a guess.


>
> By the way, is it possible with the UHD-drivers to transmit from one
> script while receiving in another script??
> I can't seem to get that working like I did with the "classic" drivers.
>
Well, with UHD, the communications are over UDP+IP, using a socket
interface, and it's likely
  that can't be shared among different processes.   But, perhaps Josh
will pop up and gives us
  a quick discourse on the subject.




-- 
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org