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Hi Grahan .mmmmm 10 feet?? that could reduce your
effective height to 10feet makingi it 6dB (maybe not quite that bad) worse
than the 40 foot pole on its own. The only plus point would be if that "radial"
gives you a substantial reduction in ground loss.....which I doubt is the case.
Seriously you do need to measure it to get the best
out of a difficult situation.......no amount of urban myth will give the right
answer. Remember higher "aerial current" is no use if its going straight to
ground (like a shunt cap across the feed point) and not traversing the radiation
resistance. You want as much current as possible to flow though the
radiation resistance (the vertical bit connected to the feed point) then you
want a big cap (=low impedance) from the top of the loading coil to earth
for the "return current" (low loss resistance) Not a very technical way of
describing it :-)) even capacitance from the active pole to ground gives
some loss....the inductive top load reduces that by reducing the voltage on that
section.
Alan
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