On Jun 4, 12:55*pm, Michael Coslo wrote:


As a point of clarification, Cecil, the bottom loaded bug catcher you
refer to - is it the matching coil or the loading coil? I only knew of
mid-loaded bugcatchers.

A short whip can be fed at any point on the radiator.
In Cecil's case, I assume the coil was a true loading coil,
and not the matching coil. As per his numbers, the base
loaded was quite a bit better than the "tuner" loaded whip,
which was 12 db down from the center loaded bugcatcher.
In general, appx 3/4 the length of the whip from the base
will be the appx best location for the coil.
The higher the coil is, the better the current distribution.
But.. The higher the coil is, the more turns of wire you
need to tune. So there is a trade off of current distribution
vs coil loss due to the extra turns.
You could have the coil at 95% high, and have great
current distribution, but the losses of all the turns required
would eat you for lunch.
So... usually around 3/4 of the way up will be about the
optimum location. 1/2 way up is good, and a good compromise
between current distribution and coil losses.
For a given length whip, Reg Edwards "vertload" program
can be used to calculate the best location for the coil,
and having played with it, and using the real antennas to
compare, I think it is very close.
Also, it jives with the info and graphs used in the ARRL
antenna handbook on that subject.