Re: [Discuss-gnuradio] 8 bit samples have an odd spectrum

[Matt Ettus]

Chris Stankevitz wrote:
> Johnathan Corgan wrote:
> > You *may* be seeing an artifact of the truncation of the ADC samples.
>
> Johnathan, others:
>
> I believe this is not the case.  When I download 16 bit samples from 
> the USRP and remove the 4LSBs myself, the spectrum looks normal.  When 
> I ask the USRP for 8 bit samples, the spectrum shows a 1MHz wide sinc 
> lobe. Since it turns out the bottleneck for me is writing to the hard 
> drive, I'm happy removing the LSBs on the PC for now, but I'd love to 
> hear your ideas! 

Also, for the comparison to be valid, you need to drop the bottom 8 
bits, not 4.  Remember that while the ADCs are 12 bits, we carry 16+ 
bits of precision throughout the signal processing.

Matt