[Discuss-gnuradio] First project: Garmin Rino GPS/FRS/GMRS?

[Kevin Zembower]

Hello,

I'm very new to GNURadio and to RF exploration/hacking in general. I've 
downloaded GNURadio on my Linux system and have been successful in 
installing a couple of systems. I got the RTL-SDR USB receiver working, 
and have the gr-rds system working.

A project I thought of working on would be to try to understand and 
document the system used by Garmin Rino GPS/FRS/GMRS systems (see 
https://buy.garmin.com/en-US/US/cOnTheTrail-cTwowayRadio-p1.html). These 
systems seem to transmit the transmitter's latitude, longitude and 
altitude to all the other Rino radios using the same FRS or GMRS channel 
and squelch code. This seems to occur whenever the Push To Talk button 
is pressed. The receiver's location, as well as all the other 
transmitters, can be viewed on everyone's GPS display.

I searched for Garmin and Rino in the mailing list's archives, and 
didn't come up with anything significant. Is this idea similar to 
anything else that anyone's attempted? If not, can anyone point me to 
ideas for getting started? I'm thinking that I'll first have to capture 
the waveforms produced by keying my Rino, then see if I can discern the 
encoding of the digital information.

Thanks for any pointers anyone can think of to begin working on this system.

-Kevin