# Using USRP N200 at symbol rate 27.5 MSps

**URL:** <https://www.ruby-forum.com/t/using-usrp-n200-at-symbol-rate-27-5-msps/223886>\
**Category:** GNU Radio\
**Created:** [October 22, 2012, 3:04pm UTC](https://www.ruby-forum.com/t/using-usrp-n200-at-symbol-rate-27-5-msps/223886 "2012-10-22T15:04:15Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![aris](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/258eb7/32.png) [@aris](https://www.ruby-forum.com/u/aris)\
**Post date:** [October 22, 2012, 3:04pm UTC](https://www.ruby-forum.com/t/using-usrp-n200-at-symbol-rate-27-5-msps/223886/1 "2012-10-22T15:04:15Z")

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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

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**Author:** ![Zooz\_E](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/z/b19c9b/32.png) [@Zooz\_E](https://www.ruby-forum.com/u/Zooz_E)\
**Post date:** [October 22, 2012, 3:20pm UTC](https://www.ruby-forum.com/t/using-usrp-n200-at-symbol-rate-27-5-msps/223886/2 "2012-10-22T15:20:01Z")

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On 22 Oct 2012 09:02, Zooz E. 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.