Re: [Discuss-gnuradio] High packet error and reception problems with RFX 2400

[Syed Faisal Shah]

Hi David,

No, we haven't tried connecting the two boards using cable. What do you
mean by 40db attenuator? Is it something we can set on hardware or from
the software?

We set the signal amplitude to maximum using 

 ./benchmark_tx.py -f 2412M --bitrate 500k -v --tx-amplitude=30000

We didn't set the gain of the transmitter. How can we set the gain of the transmitter?

We tried with different rx gains, e.g.,

 ./benchmark_rx.py -f 2412M --bitrate 100k -v --rx-gain=75
but does not improve much at highest gain of 90. 

We could not find the -g option with usrp_siggen.py. So there must be
some default settings of tx gain. While looking at usrp_siggen.py, I
found this line

fg.subdev.set_gain(fg.subdev.gain_range()[1])    # set max Tx gain

and hoping that the tx gain is at maximum. Please let us know how to adjust the tx gain in usrp_siggen.py or benchmark_tx.py.

We truely appreciate your help.


Regards

SFAS

On 4/4/07, David Scaperoth <address@hidden> wrote:

On Apr 3, 2007, at 4:12 PM, Syed Faisal Shah wrote:

> Hi fellows,
>
> We just purchased USRP from Ettus equipped with daughter board RFX
> 2400. We are trying to test these boards and have following problems:
>
> 1. The benchmark_tx.py and benchmark_rx.py from the GNU radio tar
> ball 3.0.3 gave close to 100% packet error. During the experiment,
> we used the maximum gain for receiver antenna and maximum amplitude
> for transmitter.  We are transmitting wirelessly using different
> settings of center frequency from 2400 to 2475MHz and bit rate of
> 50k to 500kbps. We are using vertical antenna from Ettus for this
> band. We varied the distance between the tx and rx from few
> centimeters to 1m. At 1m, the receiver was unable to receive/decode
> any of the packets at at all. Similarly at low bit rates, the rx
> wan unable to receive/decode any of the packets. We appreciate any
> help or clue to this problem.
>

Have you tried wiring the radios together with SMA (and 40dB
attenuation)?  If nothing else, this should work flawlessly before
you move on to wireless experiments.

What was the signal strength when you had the two boards a few
centimeters from each other?  Just curious, What was the maximum gain
you used for the transmitter (i.e. how did you set it?)  Another
variable in this problem could be the setting on the Rx PGA.  Have
you modified this value?  Most people have reported success at half
of maximum.


> 2. We tried to use usrp_siggen.py and usrp_oscope.py programs to
> transmit/receive a sinusoidal signal. The oscilloscope program did
> show a sinusoid wave but the amplitude is weak and noisy. Even the
> response to the orientation and distance of the transmitter is
> random. For some orientation of the transmitter the received signal
> gets better for a moment and then goes down again.
>

What was the gain you used (-g option) for the usrp_siggen.py?  Have
you tried using SMA cables?

> Have anyone experienced this issue with RFX daughter board and
> vertical antenna? Any help will be highly appreciated.
>

For what its worth, the RFX400 / RFX900 seem to work well with
vertical antenna, and I don't see why the 2400 wouldn't either.


> Regards
>
> SFAS
>
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