AM broadcast band antennas 5/8 & 1/2 wave tall are rarely used any more.
I noticed a reduction of the tall AM towers starting about the 1960's.
An optimized half-wave design (180-195 electrical degrees) is still the
height of choice for AM broadcasters. There are many factors, including
financial, land acquisition, etc.- that preclude the use of these optimized
radiators, but given the choice, an optimized half-wave design is preferred.
Yesterday, I pointed out that these half-wave designs were preferred since
they simultaneously maximize gain at zero elevation while minimizing skywave
radiation. It would have been more correct to state that the optimized
half-wave design maximizes gain at zero elevation while simultaneously
minimizing *high-angle lobes* that are associated with radiators over about
195 degrees in height and that includes the 5/8 wave radiator (225
electrical degrees). It's the high-angle skywave component that's
destructive to AMBC listening.
Paul, W9AC
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Topband reflector - topband@contesting.com
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