Re: [Discuss-gnuradio] UHD vs. USRP2 driver questions

[Arun Pillai]

On 11/29/2011 03:37 PM, Josh Blum wrote:
> On 11/29/2011 02:38 PM, Kevin Tien wrote:
> > Hi,
> >
> > We're using USRP2s with the RFX2400 daughterboards, and we've recently
> > switched from the old USRP drivers to the UHD drivers as per general
> > recommendation. However, we've run into a few problems that have us
> > stumped:
> >
> > 1) Previously, our receiver gains were set to 0 dB and we had no
> > problem receiving a signal with>30 or 40 dB SNR. However, now the UHD
> > receiver blocks need specified gain around 30 or 40 dB to achieve this
> > same performance; did baseline values change?
>
> Are you selecting the correct antenna? Its possible the default RX
> antenna setting is different.

Yes, I believe the default under the old usrp drivers was "TX/RX". The 
default under the new setup is "RX2". You can make a call 
usrp->set_rx_antenna("TX/RX"). That should, in theory, restore the old 
behavior (although I've seen what might be unpredictable behavior in 
this mode - I don't know for sure though) unless you have some full 
duplex shenanigans going on. Alternatively, you can just screw on an 
antenna on the RX2 port and you should see a strong signal, which is the 
approach I often use.

Arun