> All those bug catcher sheet metal hats mounted right on the
> loading coils at the bottom of a long whip? Bad idea.
>
> 73 Tom
I have a W6HIQ mobile antenna, the 4 inch, 160 meter
version. Because of tooling limitations, the coil is
limited to something like 12 inches. With the wire size
W6HIQ chose, there isn't quite enough inductance to get
down to 1.8 MHz with a 102 inch whip. (After I bought
this antenna, a 5 inch version was introduced that has
sufficient inductance to get down to 1.8 MHz).
I mount a capacitance hat a foot above the coil. This
is a crutch to get the minimum frequency from 2 MHz to
1.8 MHz by lowering the self resonant frequency of the coil.
Tom is correct that this is not helpful, but it gets me
on the air on 160. So when you see one of those hats, think
of it as a compromise, not an optimum system. It would be
better to use a "helper coil" on top of the motorized one, but
then I would have to remove the helper coil to use the higher
bands. OTOH, the capacitive hat becomes increasingly irrelevant as
the frequency goes up.
Rick N6RK
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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