> Date: Mon, 06 Dec 1999 10:37:48 -0600
> From: "Kris Mraz, N5KM" <firstname.lastname@example.org>
> Subject: [TowerTalk] Influence of tower in the near field
> Can the influence of a tower in the near field of an 80m array really
> be removed by detuning the tower?
> I know that there are methods of detuning a tower to make it
> invisible but I'd like to hear how affective it really is. Can those
> of you who have done this provide any anecdotal evidence one way or
> the other?
Any floating conductor much over a quarter wavelength will have substantial
coupling. If the conductor is grounded, then it only has to be somewhat
more than 1/8 WL. Simply "detuning" a long tower away from resonance doesn't
keep current from flowing; it merely changes the phase, as in tuning
a Yagi element to be a reflector or director. To keep my 40 meter
phased array from being affected by nearby 80 and 160 verticals, I have
had to break those verticals up into 30 foot sections with insulators
which are bridged with relays that close when on 80 and 160. I modeled
this with EZNEC. The array is under constuction so no physical measurements
yet. When on 80, the 40 meter verticals float from ground.
Rick Karlquist N6RK
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