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Re: [TowerTalk] Rohn towers

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Rohn towers
From: Patrick Greenlee <patrick_g@windstream.net>
Date: Wed, 13 May 2015 07:34:34 -0500
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Thanks to everyone who offered information and opinions regarding various aspects of mast material sizing, economics, procurement, sources and whatever else I might be forgetting to list just now.

My K7NV prop-pitch motor rotator conversion is in hand. Kurt set it up for a 2 inch mast and supplied me with specs for my guidance.

A 2.0" Dia x .250" wall 1026 DOM mast (yield = 85 Ksi) has a safety factor of 2.57 for a DB42 antenna (38.9 SqFt Effective Area) mounted 2 feet above the tower top when the tower top is 94 feet above ground. This is per ANSI/TIA-222-G, Exposure Zone C, on flat terrain in Pottawatomie County, OK which is a 90 Mph wind speed zone.

My passing interest in 0.375 material was to gain strength without increasing OD (where increasing OD would be better economics if I didn't have a rotator set up for 2 inch) I don't really need more strength if I don't extend the mast much. The 0.375 material would allow a little more extension with the same safety margin but isn't a real issue, just me dreaming of gilding the lily. Due diligence would be to use Kurts numbers and stop flailing around.

Thanks again for everyone's input.

Patrick   NJ5G
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