Mike W0BTU wrote:
... how about 1/2 wave monopoles, or monopoles between 90 and 180 degrees?
Could they be useful at any distance on 160?
All monopoles of all electrical heights of 5/8WL and less _radiate_
(launch) maximum relative field (E/Emax) in the horizontal plane --
regardless of earth conductivity at/near the radiator site, and regardless
of the r-f loss in the ground system in use.
So if one defines "takeoff angle" as being the elevation angle producing the
highest radiated field, then for all base-fed, unloaded, vertical monopoles
that angle would be zero degrees.
The shape of the elevation pattern of a monopole seen in a NEC far-field
analysis shows what remains of the original radiated fields at an ~infinite
distance over a flat, ~infinite ground plane. It doesn't show the fields
radiated in the first place by the monopole.
To see them, one needs to do a NEC surface wave analysis for an h-distance
within several wavelengths of the monopole. The radiation toward all
elevation angles greater than a few tenths of a degree seen in the NEC
"surface wave" plot, are, in reality, space waves. Those fields are
greatest at the lowest elevation angles, and are capable of reaching the
ionosphere to provide the greatest single-hop coverage range in the HF band,
and below.
The elevation patterns of monopoles with heights between 90 and 180 degrees
will lie between the 90- and 180-degree patterns shown in the link below.
Radiators between 90 and 180 degrees in height would be useful on 160,
although high-angle radiation is reduced when going from 90 to 180 degrees,
and that will reduce the skywave fields most useful for short paths.
http://i62.photobucket.com/albums/h85/rfry-100/MWElPatComparison.jpg
R. Fry
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Topband reflector - topband@contesting.com
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