Re: [Discuss-gnuradio] ADC calibration

[Daniel Halperin]

On Fri, 13 Aug 2010, Matt Ettus wrote:

> On 08/13/2010 12:14 PM, Daniel Halperin wrote:
> >  On Tue, 10 Aug 2010, Matt Ettus wrote:
> >
> > >  When using a BasicRX or LFRX with the PGA set at 0dB gain (USRP1
> > >  only), +10dBm is full scale on the ADC. On the USRP2 full scale on the
> > >  ADC is full scale when it gets back into gnu radio. On the USRP1 full
> > >  scale on the ADC is (1.67/2) times full scale due to the gain of the
> > >  CORDIC.
> > > 
> > >  +10dBm = 2Vpp = 1 Vpeak = 0.7 Vrms
> > > 
> > >  With other daughterboards you will need to calibrate at the frequency
> > >  of interest.
> >
> >  Thanks, that's helpful. However, I can't quite make the math work:
> >
> >  P = V^2/R ; 0.01 W = 1^2 / R ; R = 100 Ohms.
>
>
> RMS power = Vpeak^2 / (2*R)
> RMS power = Vrms^2 / R

... so as long as I don't send a pure DC signal (which presumably I can't 
b/c there will be filters so the device doesn't support it anyway) I 
should be using RMS power to account for the carrier wave variation?

Makes sense.

Thanks,
Dan