> Since everyone is talking about Capacitive Loading: I have been using
> a vertical, 27.5 foot high with a Cap Hat ( 6 foot Square) and a
> loading coil at 22' up. I have 30, 25' radials.
Good idea for limited space, but we should remember this.
When the antenna has a large hat capacitance, compared to the
distributed capacitance of the structure, there is no reason at all to
put the coil high in the structure.
Current distribution will be essentially the same no matter where
you put the coil, even when the antenna is FAR from self-
resonance with the hat. It is a capacitance ratio problem of the
distributed impedance and hat capacitance, not a resonance
problem.
It is a old husband's tale that current drops in the coil, probably
based on the fact that current tapers rapidly above the coil in a
system without a loading hat at the top. The inductor changes the
voltage, not the current, as it brings the current and voltage into
phase in the series-tuned circuit formed by the antenna and loading
coil.
We can make life easy on ourself if we simply use a large hat and
put the coil at the base, where it can do double duty with
impedance matching and we can reach it easily for adjustment.
73, Tom W8JI
W8JI@contesting.com
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