I really DO have 80m verticals that are 1/2 wave apart. (incidentally I
share the radial fields with the 160m antennas which are 1/4 wave apart)
So the question remains, how to properly feed phased verticals that are
physically 1/2 wave apart>>>>
If It was my array, I'd add an element in the middle hanging from a catenary
rope.
One problem with 1/2 wave spacing is the distance is too wide for effective
end-fire (out-of-phase) gain, and not quite wide enough for best broadside
(in phase) gain. More important, you cannot obtain a unidirectional
pattern.
You might consider adding a third parasitic element midway. With a minimum
of hardware, this would give you a simple reversable 80 M unidirectional
pattern in the same directions as the 160 elements. You could also still
have broadside bidirectional and endfire bidirectional, so you would have
two unidirectional patterns and two bi directional patterns with no more
than a inverting transformer and a switch.
Of course SWR would be a slight issue, but tolerable with some planning.
Mutual coupling would cause impedances to change with directions.
Otherwise, all it takes is an inverting transformer and a relay to flip
between bidirectional patterns.
73 Tom
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