[Discuss-gnuradio] benchmark_xx.py Transmits Images at +/- 0.5MHz When Center Freq Is 2.4GHz [USRP N200 and XCVR2450]

[jasonatran]

Hi All,

I have a pair of USRP N200s with XCVR2450 daughterboards running the latest
GNU Radio version with UHD. This is an odd problem, but I'm wondering if
anyone has seen this before.

When I run the benchmark_rx.py/benchmark_tx.py specified at 2.4GHz, the
transmitter is transmitting images of lower magnitude at +/- 0.5MHz, and the
receiver isn't able to decode any radio packets. Some frames are received,
but they are all "ok=FALSE" with the lengths lower than the length of the
actual packet sent. These images persist when I set the XCVR2450's to tx/rx
within its specified frequency range. 

note: the benchmark scripts are from
~/gnuradio/gr-digital/examples/narrowband/

However, when I run the benchmark scripts at "--freq 0" on both sides, the
transmitter says it is automatically set to "4800MHz" (although this is
outside of the XCVR2450's range), and the receiver says it is automatically
set to "2400MHz." Somehow, the transmitter is transmitting at 2.4GHz and the
receiver is tuned to 2.4GHz. The signal is clean, and there are no images in
sight. I used both uhd_fft.py and a spectrum analyzer to check.

Does anyone have any idea what's going on? 

-Jason
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