Re: [Discuss-gnuradio] RDS reception

[Andrew Davis]

The CGRAN RDS code seems abandoned, I'm thinking about cloning it to
github so it can be converted to UHD and Cmake and fixed up.

On Fri, Feb 24, 2012 at 1:31 PM,  <address@hidden> wrote:
> I don't know about having it inside the main codebase, but converting it to
> use the CMake build system would be good, since it didn't really understand
> how to place its python files into a filesystem that uses
> /usr/local/lib64--so I had to move them manually.
>
> -Marcus
>
>
>
> On Fri, 24 Feb 2012 10:23:48 -0800, Rafael Diniz wrote:
>
> It would be great to have the rds code inside the gnuradio tree instead of
> in a separate cgran project!
> ; )
>
> I don't know why, but when I tried the cgran rds code, the grc example
> worked much better then the python one.
>
> Best regards,
> Rafael Diniz
>
>
>
> Actually, I'm using the blks2 WBFM block, which I believe is a PLL
> demodulator.
>
> Both of my "test" stations are actually roughly 100km
> away from me, broadcasting from a high point in the Ottawa Valley.
>
> One
> station comes in about 10dB stronger than the other, although both have
> an ERP of about 100kW, and both are located on the same transmit tower.
>
>
> I'll send you my 'stuff' once I'm more comfortable with it. The audio
> quality is actually reasonably good, so I think the FM demodulator
> portion is just fine.
>
> -Marcus
>
> On Fri, 24 Feb 2012 11:12:28 -0500,
> Andrew Davis wrote:
>
> I think the problems with SNR is with the FM
>
> Demod, my car stereo can
>
> get RDS as the station fades 40 miles away,
>
> but with my USRP has
>
> trouble picking up the stereo pilot from a 50kw
>
> station one mile away
>
> ( -10dBm ). FM demod is hard for software ( I
>
> think GNUradio just uses
>
> a zero-crossing detector ).
>
> Do you have
>
> the code, I would love to test it.
>
> On Thu, Feb 23, 2012 at 11:33
>
> PM, Marcus D. Leech wrote:
>
> I managed to get gr-rds built tonight, and
>
> was able to test it planted inside my FM receiver. Even for a local
> station, there are *lots* of errors, and more distant stations get even
> more. I'm going to play around a bit with filter bandwidths, etc, to see
> if I can improve it. Looking at the modulation technique, it's no big
> surprise--they use a bi-phase baseband coding (basically like
> differential Manchester), that drives a DSB-SC modulator with a carrier
> at 57kHz. But that signal is generally about 20dB below the other audio
> sub-channels on the FM demodulator output. So the SNR is generally
> *terrible*. I'm rather surprised, after looking at it, that anyone
> bother deploying RDS. It seems utterly crappy. It's generally broadcast
> with fairly-low SNR, and there's no FEC built in, only CRC. I re-jigged
> the XML for the demodulator part so you can reset the demodulator state
> machine from within a GRC flow-graph (there was a reset() method on the
> demod, but it wasn't exposed within the XML framework for GRC). Also, I
> may re-jig the decoder portion--it currently injects decoded frames into
> a message queue and to stdout. Might be useful to do other things with
> those messages. Like is there a simple way to have a message dequeuer
> within a GRC flow-graph so that one could stuff messages into a
> variable? -- Principal Investigator Shirleys Bay Radio Astronomy
> Consortium http://www.sbrac.org [1]
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