Re: [Discuss-gnuradio] Using USRP N200 at symbol rate 27.5 MSps

[mleech]

On 22 Oct 2012 09:02, Zooz Engineer wrote:

Dear All,

I have purchased 3 USRPs (N200) and set them up. I am intending to implement a satellite receiver by connecting a board to the output of an LNB (satellite dish). I am using the daughterboard DBSRX2  and I need to used a symbol rate of 27.5 MSps ( compliant to the standard). For testing purpose, I connected a USRP source to a graphical FFT sink and ran GNURadio. Each time I run GNURadio, I receive a warning:   

The hardware does not support the requested RX sample rate:
    Target sample rate: 27.500000 MSps
    Actual sample rate: 25.000000 MSps

I understand now that to achieve what I want, samples must be taken in 8 bit format in stead of 16. However, I have no clue of how to do this in GNURadio. I changed the wire format to 8 bit but the warning keeps showing up.

Any ideas or suggestions, please?

Thanks a lot.

Zooz

The USRP family use strict integer decimation -- they don't have built-in fractional interpolators.

So the requested sample rate has to be an integer divisor of the input sample rate, which in the case of the N2XX is 100Msps.