Here's another testimonial about why NOT to
follow the Rohn guying illustrations (top guy below
the top of your tower) when stacking large antennas
above the top of your tower.
If you plan on using a long rotating mast above your
tower, you need to get the top guys as high as possible.
Another set of guys at the rotor provides even more
support for the bending moment applied to the tower.
The lower the rotor in the tower, the less the stress
on the tower.
Don't hold your breath waiting for Rohn
to come out with recommended guying / loading for
extended masts. Looks like we are on our own to
either calculate the effects or hire a PE to do it for us.
Anecdotal evidence tells us that adding extra loading
in the form of side mounted antennas seems to work
but overloading the TOP of a tower with guys placed
below the top is asking for trouble.
de Tom N4KG
--------- Forwarded message ----------
From: "Patrick Barkey" <PBARKEY@gw.bsu.edu>
Date: Thu, 23 Dec 1999
Subject: Re: [TowerTalk] ROHN SPECIFICATIONS
>> One of locals had a Force 12 6L20 (8.3 sq ft) mounted
above a Force 12 2L40 / 2L80 (13 sq. ft.) on 130 ft of
Rohn 45 with the top guy 9 ft below the top of the tower.
The rotor was approximately 5 ft down from the top of the
N8JW in Lansing had a 3 el 40 and a 205BA on Rohn 45
with something like this arrangement. E.g., antennas above
130 feet, rotor at 125 feet, top guy at 122 feet.
The wind practically twisted the top of the tower off.
Lucky for him, it didn't break, it just twisted about 20
degrees (breaking almost all the welds) and looking
very, very ugly.
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