From: charlie-cunningham@nc.rr.com
Could you support a vertical 1/2 wave for 160 with aballoon?
You could end -feed it at the base through a 1/4 wave of 450 ohm
ladder line and it would be a FEARSOME 160 antenna! And the whole radial issue
goes away!!
I've operated a vertical 1/2 wave for 40m this way with
GREAT success!...
Probably would be a great antenna as long as the bottom end is elevated well
above ground, basically forming a vertically oriented end-fed zepp, something
that might actually be feasible with balloon support if the winds are calm.
But feeding a half wave vertical with the base near the ground still results
in substantial ground losses without a radial system. True, it may be
self-resonant and not depend on the ground plane to supply the "missing half",
but with the presence of lossy earth in the close vicinity of the radiating
element, much of the rf power is wasted warming the earthworms, as the earth
and its resistive loss provides the majority the return path of rf currents to
the antenna base.
Another way of looking at it is to think of the ground radial system as a
highly conductive shield inserted between the lossy earth and the radiating
antenna, carrying the return currents while by-passing most of the ground
resistance in the return path.
Don k4kyv
_______________________________________________
Topband reflector - topband@contesting.com
|