Re: [Discuss-gnuradio] Moon Bounce Experiment

[Marcus D. Leech]

On 10/20/2010 07:13 PM, Joseph Craig wrote:
> I have managed to install gnuradio and run usrp_fft.py with success!
>
> Now for the questions...
>
> 1)  I'm always seeing...  "Exception RuntimeError: 'maximum recursion depth 
> exceeded while calling a Python object' in <type 'exception.AttributeError'> 
> ignored ".  What does this mean, and how to fix it?
>   
In what application are you seeing this error?

> 2)  How do I save the I/Q stream to disk?  I'm interested in the maximum bit 
> resolution for the best dynamic range.  I just want the raw time samples.
>   
You should investigate gnuradio-companion (GRC), which allows you to put
a signal processing
  graph together graphically--like LEGO building blocks.  You can very
easily put together a
  "baseband recorder" application in about 5 minutes this way.

> 3)  Some of the examples (like usrp_wfm_rcv.py) spit out "...aUaUaUaUaU..." 
> to the console and the sound is choppy.  What does this mean, and is there a 
> way to turn it off?
>   
It means that you're experiencing a audio underrun, likely because your
processing chain
  can't "keep up".  Perhaps because you haven't specified a high enough
decimation, and
  the chain is trying to keep up with a unpleasantly-large torrent of data.

> 4)  Is it possible to tweak parameters such as quadrature downconverter 
> bandwidth/decimation, etc?
>
> thanks,
> Joe Craig
>
>   
Yes, absolutely.  Most of the example programs take a "-d" option that
controls decimation
  in the USRP hardware. For example, if you only wanted 1MHz bandwidth,
you'd use a
  "-d" option to the examples (like usrp_fft.py) of "-d 64", which will
give you 1Msps of
  complex samples between the USRP and the host--because the A/D in the
USRP is
  64Msps.  For the USRP2, the A/D operates at 100Msps, so you'd need to
adjust your
  decimation appropriately.

You should keep in mind that except for trivial algorithms at modest
bandwidths, you'll need
  a fairly-decent computer to get the best results from your Gnu Radio
experiments.  Although
  I think you mentioned that at first you only want to record baseband
data to disk at 1Msps,
  I'm guessing you'll want to go beyond that at some point.

I'd explore gnuradio-companion as well.

Good luck!

-- 
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org