I know that the idea of the top load is to get more capacity in the air.
owever, I have read an article somewhere about toploads of a short vertical
being equipped with coils to improve or to "lengthen" the top load wires
electrically. Any experience with that? Would that do any good?
Geri, DK8KW (W1KW)
That is effectively what I do with a coil at the top of the vertical
section, before the three parallel top wires. The positive effect of
raising the current higher up the vertical section must be balanced
against the losses from the coil. It certainly works for me, and I have
tried it both at home where the vertical section is close to the house,
and portable in an open field. There is, however, an argument that
maximum benefit is when the lower part of the vertical has some local
screening by buildings and trees. It's worth a try.
I have described my light-weight loading coil here before but if anyone
wants it again, I will post it on my web site or e-mail direct.
Incidentally, I have had great success using my inverted-L on 160m by
using two coils - one at the top of the vertical, and one a few metres
along the horizontal. This seemed to work better than a single top coil.
I am not sure why, but it may have increased the amount of current in
the short horizontal section between the two coils and tailored the
angle of radiation to just what was needed. Not necessarily what we want
at LF, but again well worth a try. If we lose the will to experiment
"outside the box" we might as well give up.
--
Mike, G3XDV
IO91VT
http://www.dennison.demon.co.uk/activity.htm
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