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[TowerTalk] Breaking up guys

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Subject: [TowerTalk] Breaking up guys
From: (John Brosnahan)
Date: Tue, 28 Apr 1998 06:37:08 -0600 (MDT)
>How would you model the wire loops through the insulators? As loads 
>of  a certain capacitance (that's all I can think of doing!)? If so, 
>what capacitance?

Or short lengths of a larger diameter wire.

>That's what I do, always trying to keep the wires shorter than 1/8 wl 
>on the band of interest when within 1/2 wl of the antenna.

There are two main ways of detuning an antenna with guy wires.
1)  Guy wires that are resonant anywhere in the vicinity of the 
2)  Guy wires that are non-reosnant but very close to the
elements--even short wires can capacitively couple and detune
a parasitic element.  You can model this affect in a NEC-based program
by introducing a very short element and bringing it into close proximity
of another element and watch the antenna's performance change.
A conductive cross-boom used to support side guys is a prime
example of the problem--but if you keep the spacing to a couple
of feet or more the effect is minimal

>502 D insulators are only $2.25 each brand new from Porcelean 
>Products, and 1/4 inch preforms are much less than $2.00 (I've 
>found them as cheap as $.79 each in bulk) from utility supply houses. 
>EHS 1/4 inch guy line is a few cents a foot from utility suppliers 
>(yes, they sell EHS if you well as lower strength grades).

Be careful about buying preforms from a utility company--their
is a difference between guy grips and big grips and the utility
company will sell you guy grips which aren't rated for tower work.
They will work but don't have the same safety factor as the big

73  John  W0UN

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