-- You're circling in a thermal, having gone downwind with it. There are some short trees and a powerline at the end of the field next to where you're standing but you can still see your plane OK to fly it.
-- There's a convenient hill and small ridge at one end. The hill's one of those extinct volcanic plugs so it looks like a minature volcano with a water tank on it -- about 250' high. Its a good place to fly at, over or round the side of. Until a power field was redevloped if you got behind that hill you could be shot down by someone at that field.
These are real examples. The power law only works in "free space" (literally, "space"). Everywhere else has trees, hills, power lines and so on. Once the signal gets to our receiver through more than one path its strengh will vary considerably becuase the different versions reflected of everything will tend to add together or cancel each other out.
I don't think exotic technology will save us just yet. If we go up in frequency to accommodate the extra bandwidth needed by data radios then we're going to have even more problems with signal cancellations due to reflections. There's a technology called MIMO that may help us -- it stands for "Multiple Input, Multiple Output" (a fancy way of saying "use two, three or more radios at the same time") but its too exotic for us at the moment.
Maybe the answer is to put two radios in the plane (a 72 and a 50 MHz?) and merge the outputs in a microcomputer.
Martin Usher
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