Lloyd Berg N9LB wrote:
There were numerous technical write ups about stations who wanted the
maximum theoretical ground wave signal and spent big bucks to put up 5/8
wave verticals. They were always disappointed in the unexpectedly reduced
coverage area that resulted. Most of the reasoning for this unexpected
negative result was attributed to the minor high-angle lobe produced by the
5/8 wave coming back down and interfering with the main lower angle signal.
As a result, those station who had experimented with 5/8 wave towers
usually reduced them to 1/2 wave or less.
Note that the above effects are not present for AM BCB stations operating
with fairly low power (say 5 kW and less), and/or on higher BC frequencies
and/or where earth conductivity is poor.
In those cases the groundwave has already fallen below the ambient r-f noise
level within the radius where those high-angle skywaves start returning to
the earth -- so no self-interference occurs.
R. Fry
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Topband reflector - topband@contesting.com
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