Dielectric loading works as well in theory, but is obviously more
difficult in practice. For grins one day I modeled an 80m vertical (fed
against a couple of radials) with the vertical portion being 3 inch
diameter PVC with a wire running down the center of it. By pumping DI
water (relative dielectric constant about 3.0 if I remember correctly)
in from the base of the tube I could shift the resonant point over 100
KHz, thereby making it somewhat tunable. I shudder to think what it
would take mechanically to support it, of course, unless I strapped it
to the side of my tower with all the attendant coupling effects of doing so.
I think people have tried similar things using salt water, except
without the wire. I think I even tried modeling that once but found the
conductive loss was too high ... don't remember for sure.
73,
Dave AB7E
On 10/20/2020 1:41 PM, jimlux wrote:
There are tons of ways to do this - most antenna designs are driven by
mechanical constraints not electrical ones. Just look at all the
schemes for loading horizontal dipoles and yagis.
There are people who have built antennas out of conductive liquids.
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