I wanted to see if anyone could provide some information on a problem with tight constraints. Given a limited power source, what kind of limitations do we face in radio communication with an object at ~40km altitude? That said, neglecting variables like geographical location, weather, interference. I'm working on a very limited power supply so providing enough energy to compensate isn't necessarily an option - or my first consideration. Lets say hypothetically that a ground station is within the payloads VHF/UHF line of sight. Are their very low power alternatives i should look into or is my only realistic option considering limited communication (again, narrowing power req.). Again, any and all input is welcome; If there's any place I'd want to hear a strangers two cents on a current objective it's here. Thank you so much.