1200 baud packet is usually sent through a audiotransmitter.
You could try APRS.

"Geoff" schreef in bericht
ups.com...
Hi, over the past year I tinkered with equipment to send video
pictures from a model aircraft to the ground. The 2.4Ghz system that I
have now is working well with very good range due in part to two patch
antenna's. The transmitter and receiver both have an audio channel
with phono sockets which are not used. Can anybody suggest a circuit
design which would convert serial data from my GPS module with a
Serial Port Profile (Spp) output socket to send down this audio
channel and be converted back on the ground?

Regards Geoff