Fw: Re: [TowerTalk] Bracketed Rohn Specs
wa4dou@juno.com
wa4dou@juno.com
Sat, 22 Jul 2000 08:29:10 -0400
Don't know if this made it through or not, so am resending it. Roy
--------- Forwarded message ----------
From: wa4dou@juno.com
To: towertalk@contesting.com
Date: Sat, 22 Jul 2000 08:10:37 -0400
Subject: Re: [TowerTalk] Bracketed Rohn Specs
Message-ID: <20000722.081233.-909033.5.wa4dou@juno.com>
Hi Jason,
This is a very interesting question. A lot of us have noted the same
thing. I'm unsure just what the answer is. If one takes the conservative
approach, then you must interpret it as requiring 2 brackets. I suppose
the "liberal" approach would be to interpret it as 1 bracket anywhere
within the distance specified "upper" and "lower." My personal opinion is
that one should stay well towards the "conservative" side of things
regarding towers in general.
Looking a the tower height above the top bracket is very instructive. A
40 footer is 10 ft. above the top bracket. At 50-80 ft. the top is 14 ft.
above the bracket. At 90 ft. its 24 ft. above the bracket and at 100 ft.
is 34 ft. above the bracket. Look at the antenna area specs. for 70 mph
from 80-100 ft. Notice how fast the allowable antenna area declines. MY
own feeling is that if you were putting a small windload on top of it,
like 3 sq ft. or less, that you will be fine. I personally would not even
consider putting a tribander on it( because theres speculation that
windloading specs from amateur antenna mfgs. may need to be scaled up by
a factor of 1.5 to arrive at the same specs. that Rohn uses) Depends on
the likelihood of your having windspeeds of 90 mph or more to deal with.
In any event, i'd pay close attention to the 90 ft. height and its
recommended max allowable antenna area at 70-80 mph and let that be my
guide. And i'd use the "heavy duty" tvro bracket, not the universal ones.
Good luck ! 73 Roy WA4DOU
p.s. a lot of liberties get taken with towers and specs. Sometimes folks
get away with it for a very long time.
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On Sat, 22 Jul 2000 10:02:01 -0400 "Jason Hissong"
<jhisson1@columbus.rr.com> writes:
>
> I was just browsing through the Rohn specs and had a question that
> you guys
> would probably know the answer to.
>
> When looking at the Rohn 25G Bracketed Specs, its states upper
> brackets at
> 30' and lower brackets at 15'. Is this an AND or and OR? i.e., do
> they
> mean that you have to have both or one or the other?
>
> If both are required, then I could not put up the tower as I cannot
> go to
> 30' for one of the brackets.
>
> If only one is required, then at 40', there would be 25' of tower
> sticking
> out the top. Would that allow me to put 25' of tower as well when
> the
> bracket is at 13'? (for a total of 38').
>
> Thanks and 73!
>
> Jason
>
> "We've all heard that a million monkeys
> banging on a million typewriters will
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>
>
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