Re: [Discuss-gnuradio] Problem setting USRP transmitting signal power

[Tom Rondeau]

On Sun, Feb 24, 2013 at 10:36 PM, warren4300137 <address@hidden> wrote:
> Hi~
>
> I found some strange problem setting USRP transmitting signal power. The
> method I change the transmit power is to use a constant to multiply the
> signals. the problem is that I use bigger constant like 2.0, the SNR value i
> calculate is lower than using constant like 1.0. the transmit signal values
> are 0.005,-0.005. my experiment platform is USRP N210 plus motherboard
> RFX2400. Is there anything wrong or there are better method to setting USRP
> transmiting power?
>
> thanks!!!

The USRPs take in normalized signals, so you want to scale your
signals to +/-1 at most. If you want increased power, adjust the gain
of the USRP itself.

The reason you're seeing a bad signal as you increase the amplitude is
that you are causing nonlinearities in the hardware from a signal
that's too large. So even though the USRP will take in a +1 signal,
you'll want to back off some to keep the signal in the linear range of
the transmitter.

Tom