Re: [Discuss-gnuradio] USRP/LFRX ADC Saturation and Range

[Sebastiaan Heunis]

Hi Dan

I tried similar experiments to determine what sample level corresponds
to saturation when using a BasicRX.  I think the maximum sample level
that I got to was around 8000->-8000 when using a 10dBm input.  I
guess this might also be dependent on the decimation in the CIC, etc.
I've also noticed that the ADC doesn't clip at saturation.  The gain
just becomes much smaller.

One thing that you might try is the following (just a suggestion).
Connect a signal generator to your USRP.  Then use an FFT sink to
display your signal.  Set it so that the y-axis resolution is 1dB.
Now you can vary your input signal and see where a 1dB change in input
signal does no longer correspond to a 1dB change in the sampled
signal.  If you digitise an input signal at this level, you should
have the maximum sample value before saturation.

As I've said, I'll do the Icarus simulations sometime and see what the
maximum sample value is.

Sebastiaan