RDS fun and hello from a new user


Months ago I bought a USRP. Nice piece of Hardware but I did not really
dive into GNURadio until this weekend. Still learning about it. I am
also busy maintaining software that decodes Trunked Radio Control
Channels and LTR variants like NTS Passport.

I am a Boston area Ham and member of AMSAT. Seems like a number of
AMSAT members are on the list.

I am interested in RDS (also called RDBS here) so I downloaded the
latest code from SVN. I merged the code posted on the list and got it
all compiled.

I was able to decode a couple of stations but the current code seemed to
miss a number of strong local stations, I looked over the code and the
RDBS standard. I fixed a few minor bugs like the RT strings not being
stored properly. I even added decoding of the Callsign for RDBS. I
have to put in a option for RDS/RBDS.

I noticed the RDBS standard recommends looking for two good 26 bit words
with sequential offset words. So I changed the sync to look for two
good words with A & B offsets. This improved things greatly and I can
copy alot more RDS streams with quick sync up times.

Now some stations are solid but the decoder will drift in and out of
sync on others. It seems to be slipping a half bit. I also found the
gain adjustment can be critical when using usrp_wfm_rcv_pll_rds.py It
also seems a pilot tone is required for the decoder to work and one
station here has RDS without a stereo subcarrier. I want to try using
another FM detector besides the PLL one.

73 Eric