Re: [Discuss-gnuradio] Changes from 3.1 to 3.2?

[Matt Ettus]

Mikael Olofsson wrote:
> Greetings,
>
> I have just upgraded from GNU Radio 3.1 to 3.2. At the same time I 
> upgraded from Ubuntu 8.04 to Ubuntu 9.04. The hardware setup is a USRP1 
> with an LFTX daughterboard.
>
> Under the previous setup (8.04+3.1), I could generate signals with an 
> amplitude up to approx 1V. Above that the signal was severely distorted, 
> which fits very well with what I've been able to read about the hardware.
>
> With the new setup (9.04+3.2), the same code generates signals with an 
> amplitude of approx 0.28V, and above that the signal again is severely 
> distorted.


The old Python code has a line that sets the gain to midpoint, but it is 
conditionalized out, leaving it at the maximum.  The current C++ db code 
sets it to midpoint in the constructor.

.28V is roughly 10 dB down.  The default is now -10 dB, which is the 
midpoint between 0 dB and -20dB.


You need to send a call to set_gain to set it back to the maximum of 0 dB.

Matt