The ground station is the easiest part to assemble. Since I am using the APRS system to transmit the data, I need a radio, APRS capable TNC, and something to display the data on.

The Kenwood TH-D7A handles the radio and TNC requirements all in one simple package. Very handy. The only problem is that convienince comes with a $400 price tag. Ouch. But it is cute. :-)

Display of data can be handled two ways. The first and simplest is to connect another GPS unit to the TH-D7A. When the TH-D7A receives an APRS packet, it sends that information to the attached GPS receiver as a waypoint. If the GPS receiver is capable of handling this information (not all are. The Etrex Summit can't and the Etrex Vista can) you can use the goto waypoint capabilities of the receiver to walk (or drive) to your rocket.

APRS ground station. Garmin Etrex Vista on left and Kenwood TH-D7A on right.

If you have downloaded the topographic maps of the launch area to your GPS unit, then navigation is easy.

The second option (or use in conjunction with the first) is to attach a PC or Palm computer running an APRS program. This provides more information and flexibility than using just a GPS.

The only thing you need to build are the cables to connect everything together. The TH-D7A comes with a pair of connectors for the GPS and PC ports but you still need a cable. Because the Etrex uses a funky custom connector, it is best to purchase this. The simple way to handle the problem is to buy an extra GPS to PC data cable. Cut it in half and wire the connectors from TH-D7A to the ends. You then have a cable to connect to the GPS and another to connect to a PC.