pure software RDS?

i'm a software programmer that is new to RDS/RBDS for broadcasting data
with FM.

wondering if it would be possible to write a pure RDS decoder. e.g. to
have a USB FM tuner hooked up to my computer and getting the audio
stream into my own application. then having the application do audio
processing to retrieve the RDS commands and decode them. or will i need
special hardware?

Thanks,
casey

"kcchesnut" <casey@brains-n-brawn.com> wrote in message
news:1141356031.989294.299260@z34g2000cwc.googlegroups.com...
> i'm a software programmer that is new to RDS/RBDS for broadcasting data
> with FM.
>
> wondering if it would be possible to write a pure RDS decoder. e.g. to
> have a USB FM tuner hooked up to my computer and getting the audio
> stream into my own application. then having the application do audio
> processing to retrieve the RDS commands and decode them. or will i need
> special hardware?
>
> Thanks,
> casey
>

I don't think so because RDS is at too high a frequency for regular fm
radios to pass on. You need direct access to the 200 kHz wide fm modulated
signal. Once FM demodulation is applied, I believe, the rds carrier is
around 57 kHz. You need to filter that, mix it to baseband and do fsk
detection on the result.

I guess you can buy an fm radio with an RDS output, but if you're looking to
do the signal processing yourself you should look into the gnu radio. I know
I've seen other folks working on RDS with gnu radio and I've personally used
it to listen to the secondary audio channel on FM stations. It will cost you
about $500.

-Clark