> My understanding is that a 1/4 wave shorted at the top,
with one side
> tied to ground, and the other side fed, would provide a
driving point
> impedance which is transformed by the quarter wave line...
>
> While this doesn't change the ground system IR losses, it
does change
> the ratio of antenna impedance to ground system
loss....increasing
> efficiency.
>
> Am I missing something?
>
> n2ea
Hi Jim,
Folding the element does not change radiation resistance by
any meaningful definition of the term nor does it change
current flowing into the ground. Since folding the element
doesn't change ground current (or radiation resistance) it
also doesn't change ground loss.
http://www.w8ji.com/radiation_resistance.htm
The ratio of feedpoint impedance to ground resistance cannot
be used to calculate efficiency unless ALL of the antenna
current flows through the feedpoint and/or every resistance
in the system is normalized to the point where feed
resistance is measured.
That folded monopole thing is one of the most common myths
concerning verticals. No matter how many times it is buried
by measurements or basic antenna theory, it pops back up
again because a few publications printed it. Once something
is in print it takes on a life of its own.
73 Tom
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