First project: Garmin Rino GPS/FRS/GMRS?


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 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



I don’t think there’s anyone doing this. In general, I recommend
checking the PyBOMBS recipe list which contains a lot of active

For how to start, that depends a lot on your comfort level doing
wireless comms and DSP. Do you have any details on the modulation used?