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Re: [Discuss-gnuradio] RDS demodulation

From: mleech
Subject: Re: [Discuss-gnuradio] RDS demodulation
Date: Tue, 21 Feb 2012 12:33:22 -0500
User-agent: Roundcube Webmail/0.5.1

I'm not feeding it the stereo pilot.  I just use a fractional resampler to resample the few kHz at 19.0kHz/8 --this gives 4 samples/symbol into the DBPSK block.

The spectrum looks roughly correct--a double-humped structure either side of zero.

On Tue, 21 Feb 2012 12:27:54 -0500, Andrew Davis wrote:

exactly 19.0kHz/8?
Are you feeding it the stereo pilot or generating your own?

Have you tried looking at the signal with an FFT scope to see if there
is anything there or if it looks distorted or something?

On Tue, Feb 21, 2012 at 10:35 AM,  <address@hidden> wrote:
I'm having trouble demodulating the RDS signal that comes along with a lot of broadcast FM signals these days.  I know that there's "gr-rds" that has already done this, but I wanted to do my own just for personal education. I spent a lot of time yesterday playing with it, and I can't get anything but garbage bits out of the DBPSK demodulator in Gnu Radio.  I can't find a freely-available version of the RDS standard, so I've been cribbing from the nearly-impenetrable gr-rds implementation. What I've done is to carve off a few kHz around 57kHz out of the FM demodulator, downconvert to zero Hz, and then resample to exactly 19.0kHz/8, and feed that into a "Digital" DBPSK block, with symbols-per-sample=4.  I get nothing but rubbish out the back side of this, even for a strong local signal. Is there something I'm missing in the way the signal gets modulated? -Marcus _______________________________________________ Discuss-gnuradio mailing list address@hidden https://lists.gnu.org/mailman/listinfo/discuss-gnuradio


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