For various terrain and property line related reasons I have had to go shorter
than and significantly longer than the 80% with specific legs of my two towers,
as short as 65% and as long as 130%. This also has an effect on the tensioning
of the guy wires – and which needs to be taken into account.
What is often not realized until after the fact is that if your intention is to
stack multiple antennas and rotate them separately, either on sidemounts or
ring rotors, using less than ~ 80% may compromise or eliminate your ability to
stack and rotate the “in-between” antennas because they will likely get caught
in the guy wires. And, if there is not enough extra clearance, even if you can
safely rotate under the guy wires on a calm day, on a day when it is windy or
icy or both, you might not clear those same guy wires! It is quite remarkable
to see just how much those guy wires can move and bounce around in violent
T-storm or worse!
Depending on the band, length of the boom and elements, proposed height of the
antenna, heights of the guy wire attachment points and proximity to the
antenna, radius of antenna (mounted on the rotator) from the tower legs
(especially if side-mounted) and other factors, 80% may not be enough either;
but it will at least get you “in the ballpark” and give you some viable options.
73
Bob KQ2M
From: Grant Saviers
Sent: Wednesday, December 05, 2018 11:17 AM
To: [email protected] ; [email protected]
Subject: Re: [TowerTalk] guying distance
Except that a PE can change this with the proper analysis. Also, a post
plus deadman end is a way to geometrically shorten the 80%. Look at
commercial guyed towers and they often have a shorter guy anchor to base
perecent (ie steeper guy angles).
Grant KZ1W
On 12/5/2018 7:42 AM, Bill via TowerTalk wrote:
> Rohn specifies 80% of the height for their towers..25, 45, 55, 65 all the
> same.
> Bill K4XS/KH7XS
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