Radio Modems

Pacific Crest makes radio modems, principally for connecting a GPS rover with a fixed reference station to allow submeter accuracy.

I have 3 RDDR-96 "Blue Bricks". I got them at a garage sale along with a Magnavox GPS reference station Also included were two omni directional antennas, a YAGI directional and a 35 watt linear amp.

The Blue Bricks can 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. In packet mode, one radio can be the source of a data stream and several can be receivers, allowing in my case one base station and two rovers.

So far I have powered them up individually with their rubber ducky antennas attached and confirmed they transmit by tuning my Kenwood TH-6A handheld 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.