>
> Yet, isn't there a "watch out for" when using large differences of
> conductor diameters ? (like a 6" vertical and #14 top loading as to
> the real world numbers)
Yep, that's the main reason Roy included average gain in the
windows version, so you could watch for errors. You do have to
carefully look for weird results.
Turns out average gain works especially for receiving antennas, as
well as for looking for errors when modeling! What a nice feature it
is!
In this particular case the model corresponds to past
measurements and what theory predicts should happen. Nothing
funny or odd seems to be going on.
1.) The hat is the primary "current sink", rather than distributed
capacitance of the vertical section.
2.) Current is almost uniform in the vertical because most of it flows
into the hat, that makes radiation resistance high.
3.) The inductor corrects power factor equal current at each
terminal (as it should have) and can be located anywhere in the
vertical section without significant effects on performance.
4.) A thinner vertical section has less distributed capacitance,
allowing more current to flow into the hat.
Radiation resistance and bandwidth don't change much with coil
location, as expected from the above.
My mobile antennas were constructed using the same principles
above, and work very well. The low coil position allows me to use a
large coil without mechanical difficulties, bandwidth is wide, and
efficiency is high.
73, Tom W8JI
W8JI@contesting.com
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