Johnathan Corgan wrote: > On 1/24/08, Dev Ramudit <[EMAIL PROTECTED]> wrote: > >> I've been trying out the gr-sounder code to see if I can use it for >> some research. I modified it slightly and graphed the output in >> realtime. > > Let me work with you offline on this. The code does work over the > air, but it is probably not giving you what you expect. > Unfortunately, I'm tied up for a day or two. > I have been working with the sounder-code too. WHat I found is that since the clocks of the USRP boards are not synchronised you have two problems. The LO's of the RFX boards are not phase-coherent so you have an RF frequency offset between the boards of a few kHz. This results in not getting a spike but a kind of smeared out LF-modulated wave.
This problem should be much less with basicRX/TX or LFRX/TX boards The other problem is that the 64 MHz clocks are not synchronised. This produces a little smearing of your results but is much less a problem. Both problems get bigger as you lengthen the peudo-random codelength. You could solve this by using very precise (GPS-tamed) external 64 MHz clocks on both sides. You can also solve it by giving one USRP a clock-out and the other a clock-in and connecting them together (so they run of the same 64 MHz clock) This requires a clock-cable between the two USRPs so this is only feasable for short distances. An other solution I see is to extend the code with some PLL which recovers the symbol clock and uses that to compensate for both problems. I don't know what solutions Jonathan has, but I would like to know them too. Greetings, Martin _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
