Rds

GNU Radio
1

Hi

I am trying to extend the usrp_wfm_rcv_pll.py by reading the RDS
subcarrier, however I have a problem observing the subcarrier at all. I
have connected a file_sink to the fm_demod in order to see the spectrum
in Matlab. In the spectrum I can observe the L+R, L-R and pilot tone,
but no RDS subcarrier at 57kHz.

Have anyone successfully seen this channel on broadcast FM?

Is it possible that the RDS subcarrier doesnt have enough power to be
oberved with the USRP board?

best regards
erlend

2

Hi Erlend,

I think you should be able to see the subcarrier with the USRP. The
injection level of the RDS signal is typically around 1.5 to 2%, this is
substantially less than the pilot, which is typically around 9%, but it
should still be visible. Make sure you have a good signal without too
much multipath. Also, you want to double-check whether the station you
are looking at is indeed carrying RDS (not sure whether everybody does
in Norway).

If you end up writing a decoder, please drop me a line. The American
version of RDS, called RBDS, is (of course) slightly different. I’d be
interested in helping to making sure that it will work on both sides of
the Atlantic.

Cheers,
Jan

3

Erlend Barstad Strand wrote:

Is it possible that the RDS subcarrier doesnt have enough power to be
oberved with the USRP board

I see the RDS subcarrier all the time. Not every station uses it, so
you are listening to one that does.

Matt

4

Great pointer! Here is the posting:
http://www.archivum.info/[email protected]/2006-02/msg00018.html
This would be great to build on.

Cheers,
Jan

5

I seem to recall someone writing a gr-rds module a while ago. You might
check the mailing list archives. I would love to have this feature in
gnuradio. Please let me know if you need any help.

Matt