Tonight I have been testing some ham radio transceiver code written in Python/GNU Radio. It is some student project published on SourceForge. You can find the code on the project page at Sourceforge: http://sourceforge.net/projects/sdr.
After some initial difficulties I realized that the code only works if the receiver and tranmitter are mounted on side B of the USRP. After moving the LFRX and LFTX to side B, I could successfully test the receiver using CW, LSB, USB, AM and FM modes. See recording below. The dots on the progress bar are bookmarks corresponding to various parts of the test. You can safely move forward to the first one.