Can you please clarify. In which layer of the stratosphere are you alluding to. For example beaming from the moon, is very much different from to Troposphere as that is from a high mountain top.
The refraction of the atmosphere aka due to temperature variations and dust particles and weather can have huge impacts. Now if your assuming both receiving and sending devices are within the same medium height makes no difference and thus the equation becomes moot as your only talking about avoiding any ground interference from the natural conical beam pattern of wifi.--
Ain't nuthin but the blues! "Albert Collins".
Leave your troubles at the door! "Pepe Peregil" De Sevilla. Just Don't Wifi without WPA, "Yul Brenner"