I'm sending a IC-V8 (2m) up on a high altitude balloon, and was
debating on what power setting to use. Ideally, I'd go with the
higher power setting (5.5W), but due to the cold temperatures that are
encountered (even with insulation) and limited battery life (even with
a higher capacity battery), going with .5W is more reliable from a
battery life standpoint. Also, I'm using an audio sound module (not
packet radio) to relay GPS information back.

My question is: can I get clear reception using the .5W power setting,
even when the balloon is, say, 75 miles away at an altitude of 20
miles?

Thanks in advance!
Dave