At 09:39 AM 8/28/01 +0200, i4jmy@iol.it wrote:
>Since we are after the very best we can do, why not sharing also what's
>good and what's not when playing with capacitive loading ?
>After all I think that careing about the best way to apply an idea,
>expecially if good, has some merit and the opposite hasn't great.
Mauri,
That's exactly why I presented the problem to the list. This is, after all,
AMATEUR RADIO, not a military exorcise or commercial broadcast. Just a
bunch of hobbyists trying to do the best they can. Most topband ops work
with less than idea QTH's. Given the space and height restrictions MOST of
us have, shouldn't we spend some time exploring ways to optimize antennas
for this type of QTH?
It's real tempting to just hang wires off the vertical section to resonate
it. I was looking at this very solution until I did some measurements and
verified with computer modeling. Even than I wasn't sure, so asked for
verification from the list.
I think we have a consensus that drooping wires from the top of a
relatively short vertical section to a point near ground is not a good
thing. We also have consensus that a "hat" properly implemented is the best
solution. However this solution does not address the original problem, i.e.
it is not physically possible to do that!
My solution to this problem has traditionally been to use inductive
loading. Since I have the experience, ability, and most importantly, the
machine tools needed to build structurally strong loading coils and masts,
this has worked well for me. Others with different skill sets and resources
may need a different solution. Personally, I would like to explore other
options.
It would seem that a mix of "hat" and inductor may be what's called for,
but where is the dividing line? Given that a "disposable", limited space
antenna may not be able to have a hat any bigger than Tom's mobile antenna,
where do we want to put the coil? Is Q really important or is it's effects
"lost in the noise"? Questions, Questions. There is not enough time
available for me (or maybe any one person) to do the modeling required to
evaluate all the possibilities, but as a group we may be able to come up
with some better guidelines.
73,
Larry - W7IUV
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