Re: [Discuss-gnuradio] Basic USRP transmission

[mleech]

On 27 Nov 2012 13:26, Fabián Kozynski wrote:

I'm trying the USRP using GNU Radio but I cannot receive successfully. I'm using the following flowgraphs in GRC:

 

TX:

Vector Source => Packet Encoder => DPSK Mod => UHD Sink

 

RX:

UHD Source => DPSK Demod => Packet Decoder => File Sink

 

I tried using benchmark_tx and benchmark_rx and the packages got through without errors. However, in my GRC example, nothing gets written to the file. Why is that? How can I send a simple binary file through the UHD?

 

Fabián

Are you looping back to the same USRP, or different ones?

What type of daughtercards?

If looping back, are you using an attenuator?

 

I'm not looping back. I'm using two USRP's, each one with a XCVR2450. I'm transmitting at 5GHz using 200KSps, DBPSK.

 

 

The usual reason is frequency offset between sender and receiver.  The effect is worse when it's narrowband, and is also dependent on the frequency precision of the master oscillator on the USRP.  Different USRPs have different-quality master oscillators.

This is pretty normal for radio-based digital communications systems.  The RX side normally has some kind of frequency-offset compensation built in.