We made more progress on the balloon tracking electronics this weekend. We tested out the Big Red Bee tracking transmitter and made an insulated, ruggedized package for it.
Fore the GPS-based tracker, we have settled on the Byonics Tiny Track 4 APRS system. Since many GPS units do not function above 60,000 feet elevation, we are going with the special "High Altitude Build" of the Inventek ISM300 GPS module.
This unit only comes as a tiny SMD module, so we are integrating the unit, a 25mm active-patch antenna, a MAX2323 driver IC, a backup battery, and assorted other bits into a custom circuit board. Here is the prototype so far:
The board is also almost reach to etch. I found a good Eagle Cad tutorial on making ground planes, and refined the design a bit:
The 2.0 version will probably be all SMD components, but this should get us going, as we have the through-hole versions of all of these parts on hand at the shop.