Re: [Discuss-gnuradio] Re: how to setup adc_ratein grc_usrp.simple_source_c

[Eric Blossom]

On Fri, Mar 06, 2009 at 11:59:13AM +0000, feldmaus wrote:
> Josh Blum <josh <at> joshknows.com> writes:
> > Simple source exists because actual usrp api is sooo crazy. The goal of 
> > the simple source and simple sink is to provide the most useful options 
> > to the usrp user.
> 
> Thank you for your Reply.
> 
> Is it possible to make an offset so that i get the
> right dB not dBFS ?

Marcus,

To reiterate what other people have said over the past few days,
calibrating the USRP requires an understanding of all of the analog
and digital controls that are in the path, and then computing
calibration coefficients for each possible combination.  E.g.,
changing the gain would change the calibration.  Changing the ambient
temperature will change the calibration.  Changing daughterboard
types will change the calibration, changing daughterboards instances
will change the calibration.  Changing the interpolation or decimation
will change the calibration...

Spending some time with the USRP FAQ should allow you to understand
what's going on.  This diagram page, RFX-2400 specific, should help too:
http://gnuradio.org/trac/wiki/UsrpRfxDiagrams

Eric