Topband: Re: Top fed vertical
Tue, 31 Jul 2001 13:40:19 -0400
Roy, K6XK wrote:
"I like top feeding because the current is higher
above ground. This gives a better shot over high, thick trees...etc."
The current distribution in a given antenna element is independent
the location of its feed point...a common misconception.
73, Roy K6XK
If it is a misperception, it is certainly a widely held one. Perhaps
this might apply roughly for physically short verticals considerably
shorter than a quarter wave due to loading. Am I missing something
obvious here? If what Roy says is true, it should be impossible for
me to voltage feed a quarter wave vertical at ground level and force
a current node to exist a quarter wave up in the air- with appropriate
"L" or "T" wires aloft at the current node for the vertical element to
'work against' ('radials'). This would in turn mean that the Bobtail
and half square antenna family is entirely bogus and does not work
as per conventional theory. It would also mean that I should not be
able to force a current point aloft by (ignoring antenna/feedline
interaction problems) coax feeding a T or L directly at the top.
73, David K3KY
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