Some earlier posts have implied that monopoles installed at sites with poor
earth conductivity don't produce much low angle radiation. Probably this is
based on an observation of the NEC far-field pattern over poor earth, and
looking at an assumed "take-off angle" from the monopole.
However the surface-wave radiation present within the 1st km of all 160m
monopoles essentially has the same shape over the range of poor to excellent
earth conductivities. The real value of the radiated surface wave field IS
a function of earth conductivity, but the affect of conductivity on the
shape of that field is negligible. It is this region of radiation from a
monopole that produces the greatest single-hop sky waves on 160m.
The following link illustrates these pattern effects for a wide range of
conductivities, other things equal.
http://i62.photobucket.com/albums/h85/rfry-100/Monopole_Surf_Wv_Compare.jpg
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