Originally posted by Birdie
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He is also correct with the remarks re trees & buildings etc. Rain also makes a huge difference at these frequencies; see what happens to your satellite TV in a heavy rain storm.
A couple of other things that would affect range are aircraft transponder power, aircraft altitude and receiver sensitivity (not to mention antenna gain & feeder losses)
I have no idea of receiver sensitivity but I have seen figures of -90dBm at 981 MHz and -71 dBm at 1090 MHz.
Using those figures, 600Km is really pushing your luck at 1090 MHz; the theory says the received signal will be about -90dBm.
Having said that, experience has shown me that when it comes to propagation, the theory rarely matches the practice!
Some years ago, my colleagues and I provided the late King Hussein with a hand held radio (the same sort of thing supplied to police forces etc), operating on 144 MHz and he was able to talk with the people on board Spacelab. He couldn't see it but he could talk to it!
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