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Re: Topband: verticals by the sea

To: "Carl Luetzelschwab" <carlluetzelschwab@gmail.com>, <topband@contesting.com>
Subject: Re: Topband: verticals by the sea
From: "Richard Fry" <rfry@adams.net>
Reply-to: Richard Fry <rfry@adams.net>
Date: Fri, 3 Apr 2015 04:34:30 -0500
List-post: <topband@contesting.com">mailto:topband@contesting.com>
NEC modeling to determine the effects on the fields radiated by a vertical monopole when siting it near a salt-water coastline can be highly misleading if the surface wave field is not considered.

For example, the plots linked below show that for average earth conductivity the E-field at 5 degrees elevation is about 2.44 times greater in the surface wave plot than in the far-field plot, at the same horizontal distance from the radiator. Their difference is infinite in the horizontal plane.

But if this radiator was sited 1 km from the ocean, then the fields at 1 km shown in the surface wave plot would decay at nearly a 1/r rate as they propagated further on that bearing, along and over the ocean surface.

This is a much different conclusion than reached when considering only the NEC far-field analysis.

Comment/discussion is invited.

R. Fry

http://s24.postimg.org/6nchfpt1h/NEC_FF_vs_NF_Calcs.jpg
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