Radio range
Those that fly on the ham ban here in the United States can transmit with more power than what is available in a stock radio. I'm sure some of the more technically minded could come up with an amplifier to boost the output. I'm also sure you could increase the range with a better antennae on the transmitter. When Maynard Hill set the model aircraft ailtitude record back in the sixties (0ver 27,000 feet if I remember correctly), I think I remember pictures of him have a large ground mounted antennae. Keep asking and I'm sure someone can give you the information you need.