[TowerTalk] Maximum Guy Radius

[john at kk9a.com]

The 80% rule is just a recommendation, at least that seems to be the 
standard in the U.S.  A common problem is lack of space and many towers are 
installed with less than the 80% spacing.  I had a tower in Aruba with 
around 50% spacing on two of the anchors and it held up fine.  I am not a 
PE, but I believe that smaller spacing puts more stress on the tower, guy 
wires and anchors and they need to be properly engineered for this 
configuration.  I would expect that going to more than 80% spacing would put 
less stress on the tower and components.  I seem to recall one rotating 
tower component manufacture recommending 100% guy radius, for less force on 
their rings.  Using a larger guy radius also allows for more clearance for 
antennas to turn.  Unless you have a specific reason for changing the 
manufacture's recommendation, I would follow it. Since you are installing a 
substantial tower (46" face, 180' high) you will need some very large and 
expensive guy wires.  Using more guy wire than needed may be just a waste of 
money.

GL,
John KK9A




To: towertalk at contesting.com
Subject: [TowerTalk] Maximum Guy Radius
From: Dorn Hetzel <kb4eq at hetzel.org>
Date: Wed, 21 Sep 2011 09:33:28 -0400

If I have a tower of a specific fixed height that I will be erecting,
and I have plenty of room to do so, I would estimate that I should
gain *some* additional strength against wind-load by moving the
guy radius from 80% of height to 100% of height, since this will
move the guy angle closer to horizontal and reduce the down
force on the tower and increase the horizontal back-force for
a given guy tension and a given stretch in a guy due to motion
of the tower.

Can anyone comment from either a practical experience or
engineering point of view whether this estimate is sound?

73,

Dorn Hetzel
KB4EQ
kb4eq at hetzel.org
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