Hi there,
I made some decent progress but refining the parameters for the
benchmark_tx.py and benchmark_rx.py without no errors. However, I can
only transmit but I could not receive anything at the receiver side.
Could somebody suggest what might be the problem? I tried to work it
but still could not find answer on why I did not received anything.
Used code:
./benchmark_tx.py -f 400M -r 250k -S 4
and
./benchmark_rx.py -f 400M -r 250k -S 4
OS: Ubuntu 11.10 (which I read in blog said that it has some problem
with gnuradio)
Gnuradio: 3.5.0 rc 0 (which I git from master branch)
Hardware: USRP1(transmitter), USRP N210(receiver)
Machine: Lenovo T510 (transmitter), Dell Desktop
Regards,
Muhammad
A common reason for this type of problem is frequency-offset between RX
and TX. On the RX side, use uhd_fft.py to observe the spectrum
and see where the receiver thinks the peak of the spectrum is. Then
adjust your '-f' accordingly on a subsequent run of benchmark_rx.py.
Crystal oscillators aren't perfect. Even an error of a few 10s of PPM
can add up to several Khz at center frequencies in the hundreds of
MHz. Unless the receive flow-graph has a way of correcting gross
frequency error, you will have to do that manually.
This is such a common problem that I'm surprised you haven't covered it
in your coursework yet. Real radios (and radio channels) have
impairments that often aren't adequately modelled by simulations.
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
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