N4UM explained to Tom:
>The 165-175 foot length (longer than a quarter wave) raises the radiation
>resistance of the antenna to somewhere close to 50 ohms but, at the same
>time increases the inductive reactance. The capacitor is used to cancel the
>inductive reactance when the total length goes beyond a quarter wavelength.
>I use the same technique by making my "quarter wave verticals" longer than a
>quarter wave to bring their radiation resistance up to 50 ohms and then I
>tune out the additional inductive reactance by using series capacitance. I
>live in a salt water environment and do not like using expensive variable
>capacitors that are exposed to the elements. I use pieces of coax as a
>simple inexpensive substitute for variable capacitors. RG-8 runs about 30
>pf per foot. I "tune" the coax capacitor with wire cutters and seal the
>exposed end with epoxy when I get the length right. The trick is not to
>snip too much off at one time!
Presumably this is with elevated radials? I thought once close enough
to ground, radial length determined performance of return currents
(significantly reduced beyond where the radial ends) & not resonance.
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