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
> http://www.antennazoning.com/_mgxroot/page_10748.html
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.
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 <http://www.championradio.com/Gunnar-Olsen.pdf>
> http://www.championradio.com/technotes.html
>
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).
http://cellularpcs.com/gallery/displayimage.php?album=13&pos=1
http://cellularpcs.com/gallery/displayimage.php?album=13&pos=38
Here's a picture of the entire installation, about a year later.
http://cellularpcs.com/gallery/displayimage.php?album=topn&cat=-13&pos=48
jim, w6rmk
>
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