[Discuss-gnuradio] Differences in Signal Spectra between Daughtercards

[Thomas]

Hi,

I'm working on a project that requires using two receivers tuned the same frequency simultaneously. Ideally, I would use identical receivers, but I am using a TVRX card and a DBSRX card becuase those are what I have available.

I'm curious why the spectra of signals received with the TVRX seem to be more spread out than with the DBSRX. An example is shown in the link below. The upper plot is from the TVRX, and the lower plot is from the DBSRX. This signal happens to be an ATSC carrier. Both daughtercards are tuned the same frequency, and the FFT parameters and so forth are identical.

http://img23.imageshack.us/img23/3206/screenshotusrpfft2.png

Does anyone know what causes this apparent spreading and if there is anything I can do about it?

I purposely left out details of my configuration to keep this message short, but feel free to ask for more information if this isn't enough to answer my question.

Thank you,

Thomas