Aunwin, we are talking about two different things.

If I want to communicate (optimally) with another station it is important
that I know the direction and elevation angle at which to point my antenna
such that the radio beam preferentially returns to Earth in the vicinity of
the other station.

Direction is found from a map of the Earth's surface plus a magnetic
compass.

The ONLY way to find the elevation angle is to CALCULATE it from the ground
path distance between the two stations, the height of the reflecting layer,
and the number of hops along the path.

It's purely a matter of Spherical Geometry. It has nothing to do with where
your antenna happens to be pointing. Or even whether or not you have an
antenna.

All good radio engineers do it that way. Caculating formulae can be found in
practical radio engineering books. Eznec won't tell you.

Use simple program TWOHOPS to do common calculations. Results are as
accurate as the inevitably uncertain input data.
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Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
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