From: Josh Blum <address@hidden>
Sent: Wednesday, May 2, 2012 9:14 PM
Subject: Re: [Discuss-gnuradio] benchmark_xx.py Transmits Images at +/- 0.5MHz When Center Freq Is 2.4GHz [USRP N200 and XCVR2450]
On 05/02/2012 07:42 PM, jasonatran wrote:
> 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.
Do you have a screencap of the problem spectrum? Maybe from the
perspective of the receiver.
note: the benchmark
scripts are from
> 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.
Well XCVR2450 has a dual band. I think you are seeing some weirdness
with the code either trying to auto select the middle frequency, and the
actual frequency being coerced.
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