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[TowerTalk] phased triangular arrays

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Subject: [TowerTalk] phased triangular arrays
From: "Jim Jarvis" <>
Date: Thu, 06 Apr 2006 15:34:24 +0000
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I've used 3 element 90 degree spaced vertical arrays in the past,
driving 2 out of 3, running matched, equal length
feedlines to each vertical, and using one 90 degree
phasing line.  Worked fine, and gave decent f/b in 6 directions.

Here's a modelling/measuring problem, which perhaps some TT'er has
already solved.

The third element is parasitically coupled to the driven pair, and
therefore should affect the pattern.  I never had an operating impedance
bridge for 7MHz, which would allow me to intentionally detune the
third element.  So I took the empirical approach...just put it up and
noted performance.  Seemed ok.

And the question:  Has anyone considered the third tower decoupling
problem?  Is it possible that having the 'right' length of feedline
would effectively decouple the tower at the operating freq.  Maybe I
got lucky.  Has anyone modelled such an array?

Here's another possible use-case:

We know that you can feed sloping dipole arrays from a central tower,
through 3/8 wavelength feedlines to a central switch.  The reactance
of the feedlines makes the un-fed dipoles appear long...and act as
reflectors.  Why couldn't that be done with verticals, as well?  
Not as predictable a pattern as a 90 degree spaced, 90 degree fed pair..
but perhaps useful just the same.   Thoughts?  



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