On 1/8/2022 7:27 AM, CUTTER DAVID via Topband wrote:
I recall a discussion on here some years ago which proposed that, whilst being
an amazing antenna for top band, if you could achieve it, the broadcast model
was not necessarily the best use of resources for amateur purposes, on the
basis that broadcasters are mainly interested in ground wave to cover a defined
relatively short range service area, whereas amateurs a more interested in dx.
The function of radial systems under a vertical radiator is solely to
minimize loss in the very near field. That has nothing to do with the
means of propagation -- i.e., ground wave vs skywave. With directional
arrays of verticals, widely used it broadcasting as well as ham radio,
they have a second function, directly related to the first, of
controlling the nulls in the pattern by minimizing differences the
contribution of each element by making those losses as small as possible.
Radial systems in broadcasting are (or at least were) controlled because
licenses were granted on the basis of carefully controlled coverage
areas, and for protection of other stations on the same or adjacent
channels. I learned about this as an EE student, working in the
consulting office of Pete Johnson, whose practice was designing these
arrays to fit new stations into the AM band that had been full for 20
years. Pete and Carl Smith (who ran CREI) wrote FCC AM technical Rules
after WWII.
73, Jim K9YC
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