Steve
About a dozen years ago, an acquaintance of mine came up with
a similar idea, a double spiral based on the Log Spiral antenna.
Based on his experiments, he was pretty sure it as a nice
broadband radial system, and useful for temporary operation
since it was pretty easy to lay down.
He abandonded the idea after it was clear that it didn't work as well
as he'd hoped. If such a spiral is truly working like a log periodic
structure, only the inner portion will be active as a counterpoise,
and the currents will decrease to about nothing further out.
I believe your idea is roughly equivalent to one radial, but it will
be usable on many bands.
It would be interesting to see if the double-spiral works as a radial
system under a roof-mounted multiband vertical -- this is one case
where it might be a good choice.
73
Gary Breed, K9AY
--------------
I've been wondering if anyone has tried this on radials for verticals:
Taking a 500' roll of copper wire and attaching one end to the base
of the vertical and winding it in a coil shape, starting out close
to the vertical and getting larger and larger going around it making
the spacing about a few inches on each pass. Just laying it on the
ground also. For 40 meters, maybe making the total outside coil
diameter about 66 foot. I've not modeled this nor do I really know
how to correctly. Winter will be here before we know it and I am
already thinking lower bands. Any thoughts on this guys, or am I
just dreaming of not having to cut 120 radials for each element?
Good luck and Thanks!
--
FAQ on WWW: http://www.contesting.com/antennaware-faq.html
Submissions: antennaware@contesting.com
Administrative requests: antennaware-REQUEST@contesting.com
Problems: owner-antennaware@contesting.com
|