Re: [Discuss-gnuradio] tx_ofdm and rx_ofdm

[Martin Braun]

On 26.05.2014 13:03, xianda wrote:
> Hi:
>      Now I run the example(tx_ofdm and rx_ofdm) through two usrps.(The
> version of my gnuradio is 3.7.4).
>     1.But in the receive part I receive two many things like this:
> INFO: Detected an invalid packet at item 139632
> INFO: Parser returned #f

Xianda,

this questions pops up a lot on this list, and 99% of the time it means 
your RF settings are distorting your signal. Try reducing gain and 
multiplier, and make sure you get a nice spectrum before you try and 
receive (i.e. check it with uhd_fft and make sure it's rectangular).

> UHD Warning:
>      The hardware does not support the requested TX sample rate:
>      Target sample rate: 0.100000 MSps
>      Actual sample rate: 0.195312 MSps
> And the device I use is USRP N210.And I set the sample rate is  100k.
> Some days ago,someone tell me set the sample rate 100M/even number.And
> the 100k seems right,why this UHD warning?Can someone tell me what is
> the appropriate sample rate for USRP N210?Thank you very much.

If you want 100K, you need to resample on the host. A stock N210 can go 
down to 100e6/512 (i.e. what you're seeing). But that's OK, resampling 
from 200k to 100k is not too CPU-intensive if you have a decent hardware.

M