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Topband: Monopole Elev Pattern w.r.t. Earth Conductivity

To: <topband@contesting.com>
Subject: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
From: "Richard Fry" <rfry@adams.net>
Reply-to: Richard Fry <rfry@adams.net>
Date: Sat, 13 Oct 2012 16:25:47 -0500
List-post: <topband@contesting.com">mailto:topband@contesting.com>
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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