No, you definitely can't with any consistency. I've found that I can
get an text msg off and receive one at less than 5,000. But nothing is
consistent or reliable.

I'm just trying to figure out my best options for ground briefings.

Paul kgyy wrote:
Can you use the Treo at 5000 ft AGL? Just curious. I tried my Sprint
cell last week and couldn't pick up a signal at 5500.