Radio Modems
Pacific Crest sells radio modems.
I have 3 RDDR-96 "Blue Bricks". I got them at a garage sale along with a Magnavox GPS reference station
Along with the modems I got two omni directional antennas, a YAGI directional and a 35 watt linear amp.
The bricks operate in two modes, transparent and packet. In transparent mode a pair of the radios acts as a replacement for a serial cable operating at 9600 bps.
So far I have power them up individually with their rubber ducky antennas attached and confirmed they transmit by tuning my Kenwood HT to their frequency and listening the bleeps when I type.
My radios came from the factory tuned to 420 Mhz. This means that I can operate them using my amateur radio operator's technician license. It's in the 70cm band. (See http://www.arrl.org/FandES/field/regulations/bandplan.html#70cm)
The typical use for these radios is to connect
Current plan is to string a cable to the roof for the YAGI, and send out DGPS corrections from the reference station.
The rover will be a Leica 9400 or a Garmin or possibly a Trimble. Probably all three but not at the same time.