80M dipoles begin to "play well" at 90 ft. Higher is better.
An 80M rotatable dipole can be placed parallel to the boom
of a 2L 40M beam with practically ZERO interaction.
The boom of a full size 3L40 on a 48 ft boom can be gamma
or omega matched as a rotary dipole on 80M. I have done this
several times on 40M using 24 ft booms on a 3L20 and a TH6.
I see no reason it wouldn't scale to 80M with a sufficiently large
40M beam.
A low cost alternative is two 80M inverted vees at right angles
below a 40M beam. The downside is that there will be some
interaction and more earth loss due to the ends being lower.
Pull the ends out as far (high) as possible.
My friend KZ4V does quite well with an 80M inverted vee at 90
ft aimed at EA / ZL (60 / 240 degrees) and a vertically polarized
Delta Loop aimed at JA / S.A. (150 / 330 degrees).
de Tom N4KG (80M DXCC = 322 with dipoles and vertical)
On Tue, 14 Aug 2001 "J. Kincade" <w5kp@swbell.net> writes:
>
> Trolling for experience-backed opinions:
>
> Is a 75M rotatable dipole a waste of money if 92' is as high as one
> can install it? Would having it that low destroy the rotating advantage
> of the end nulls, thereby turning it into an expensive inverted V? The
> alternative, of course, is to spend the bucks on a shorty 40 at the
> 92' point instead, and hang a good 'ol cheap inverted V for 75.
>
> Thanks for the brain cell time.
>
> 73, Jerry W5KP
>
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