On 08/16/2010 09:22 PM, Ian Holland wrote:
Please disregard my last. I must have got something wrong in my testing. It now compiles, but it seems I need to use txrx_xcvr.bin instead of txrx.bin with the latest git trunk. Please correct me if this is wrong (note I have XCVR2450 as my daughterboard).
This is correct. Due to the size of the code, the xcvr was split out to its own file. Also, you are right about the prescaler.
Nonetheless, I still seem to get a time varying frequency offset between a transmitted and received BPSK waveform, when using the same local oscillator of 36 MHz at each end. In fact, about every million samples, this frequency offset disappears, then comes back getting larger, then smaller and disappears again about 1 million samples later.
>
Is this expected when using a reference different to 10 MHz? When I have used two USRP2s both locked to a 10 MHz reference, I never saw this problem.
No, you should not see that. It sounds like it is not locked, and I think the reason is loop bandwidth. The original setup is for a 10 MHz compare frequency, and you are using a 1 MHz compare frequency. This will mess up the loop dynamics by dividing the loop bandwidth by 10.
The greatest common divisor of 100 MHz and 36 MHz is 4 MHz, so I would use that for the compare frequency. Then also increase the charge pump current to the maximum. That should bring you closer to the original loop bandwidth.
Matt _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
