[Discuss-gnuradio] USRP2 Simultaneous Tx and Rx Transmit Errors

[Kyle Pearson]

Hello all,

When I try to simultaneously transmit and receive a sine wave source
on one USRP2 using GRC, there appear to be phase discontinuities in
the transmitted waveform(as if packets from the computer to the usrp2
for transmit are possibly being lost or garbled). This only occurs
when transmitting and receiving at the same time, and when I connected
the tx signal to a spectrum analyzer it showed random spurs in
addition to the expected peak from the signal. When only transmitting
the output on a spectrum analyzer confirms that the transmits properly
and when receiving a signal from a signal generator there are no
errors. This occurred even when the decimation and interpolation rate
was set to 512 and I tried a different ethernet cable but the problem
still persists.

Here's my setup:
GNU Radio rev. 10661 running on Ubuntu 8.04
Dell E6400 Laptop with P9500 processor (2.53GHz) and 4Gb RAM
1 USRP2 with LFRX and LFTX daughtercards, firmware released 3/15
USRP2 Connected directly to laptop (no router/switch)

I've attached the GRC graph and some examples of a Scope display.

If anyone has similar problems or has any ideas how to solve this,
please let me know. Also, if you can do this without the error let me
know, maybe the issue comes from the laptop.

Thanks,
Kyle

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