[Antennas] Loading inductances

Wed Jul 7 06:36:23 EDT 2004

Hi, all concerned:
A simple rule-of-thumb is to add 10% to the antenna's linear length, and
wind part of the linear length into a coil until the overall length fits
what ever physical dimension you need to acommodate.
Eg, a 1/4-wave vertical is around 66 feet tall somewhere around 80M. Start
with 73 feet of wire. If your tree-limb support is up only 45 feet, then
you'll have around 30 feet in the coil, and about 43 feet of linear antenna.
For openers, put the coil half way up. Or, put it at the base. Where ever.
Try a length of tubing as a tophat.
One of the experiments I've wanted to try in this lifetime is making the
linear length and loading coil from tape, on a form which I can run up and
down in height, the object being to get a feel for the effects of changing
the height of the load, without changing the overall length, and without all
the physical hassle (just most of it, hi) of different lengths of wire.
One of those surplus tape-wound coils would be nice to have ;o).
Hth. As always, YMMV.
73, Dave, N3HE