After a bit of research on communicating with things very high in the sky, I concluded that I had two options:
- Pay $300 for a 20mi radio
- Cellular data
The downside to using cell towers is that they have a maximum range of about 10,000ft from the surface (This is because cell towers are optimized for signals below them). The practical effect of this is that I would not be able to maintain constant telemetry for more than the first tenth of the altitude, as the balloon ought to go to upward of 80,000ft. That being said, AT&T's data coverage map of East TN and the surrounding area looked as if was practically guaranteed to land in cell tower range.
So I got a cheap 3g dongle from amazon (see parts list).
And after watching a number of representatives from a variety of providers stare with a mixture of disgust and confusion at my strange device, I finally found that AT&T was able to provide a sim card that would work.
Once that was done however, I needed to pair the dongle with linux. To that end, I found a neat little program called sakis3g. With some tweaking of the config files (of both sakis3g and wvdial) I got it working very reliably.