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Re: [TowerTalk] Setback requirements (was "permit in hand")

To: "Jim Lux" <>,"bill rubin" <>
Subject: Re: [TowerTalk] Setback requirements (was "permit in hand")
From: "jeremy-ca" <>
Date: Sun, 2 Sep 2007 14:15:00 -0400
List-post: <>

> bill rubin wrote:
>> Perhaps this will help your case,  Rohn letter stating that tower failure 
>> is
>> 1/2 to 1/3 height. see Rohn Letter on Fall Radius of a Guyed Tower at
> That's an interesting letter.
> Note, however, the "assuming the guys remain intact".. you'd have to
> show by analysis (or test<grin>) that the guy system's failure point is
> so much higher than the tower's, that the tower is guaranteed to
> collapse first.  That might not be a tough hurdle to bear, depending on
> the system.

Jim, you are assuming brand new guy wire of the type defined by the tower 
manufacturer. Ive reguyed towers installed with wire rope and Rat Shack crap 
for TV masts. Dont expect the building inspector to know the difference.

Another factor missed by those who dont live near salt water is to have salt 
laden fog or drizzle that comes many miles inland. Ive walked out of the 
house on many a morning and couls taste the salt in the fog and I'm 20 miles 
inland. After 15-20+ years even 3/16 EHS may be the weakest link by far.


> And, of course, if you have a lot that is 50 feet wide (as many are),
> that would limit you to a 50 foot tower (if you take the more
> pessimistic 1/2 the height fall radius) placed precisely in the middle
> of the lot.
>> Also see Gunnar Olsen Study 
>> <>
> Another interesting report.  One issue that might arise in the context
> of using the Olsen analysis is that many broadcast towers have multiple
> guy anchors.  The other thing is that broadcast towers are designed,
> erected, and maintained with a lot more oversight and expense.  What if
> the city says, "fine, go ahead with your tower.. We want you to hire an
> independent engineering firm to supervise the construction. Oh, and we
> want you to develop a regular inspection and maintenance plan, and file
> annual inspection reports with a certification by a P.E. that the tower
> is still structurally sound"  This is fine for a TV station putting up a
> 1000 ft tower, because they'd essentially do that anyway. Not so fine
> for a ham wanting to get a bunch of buddies over for a antenna raising
> party over Labor Day weekend.
> BUT.. this, in general, is the sort of analysis that would help make the
> case in front of a planning board.  Maybe, someone could convince a
> professor with a grad student looking for a thesis topic to do a
> rigorous analysis (with experiments) of these sorts of things, with the
> product a nice consumer friendly report.  Then you could get the "Dr.
> somebody of University of XYZ has researched just the area about which
> you are concerned, and here is their summary of findings."
> (Bear in mind though, that my inherent cynicism about local regulators
> is that they might just say, "we don't care, we don't like your antenna
> ideas, and we'll find anyway we can to prohibit it. By the way, have you
> surveyed your proposed construction site for Native American remains?
> Oh, and while you're at it, do you have a survey to prove it's not a
> riparian habitat? And, what about the Environmental Impact Study or the
> analysis (negative declaration) showing you don't need one.  You have,
> of course, done the required traffic pattern impact study, haven't you?
> And what about the fence to keep people outside the RF exposure limit."
>   You might laugh, but all this, and more, was faced by a local radio
> station looking to put up a 30 foot(!) high mast for a FM broadcast
> transmitter.  We're talking about something that literally looks like a
> flagpole with a funny set of rods on top on the side of a hill hundreds
> of feet from the nearest public road or building (heck, the underground
> transmitter is 700 ft away, talk about a long feedline).
> Here's a picture of the entire installation, about a year later.
> jim, w6rmk
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