Hello Again,
I really didn't want to get into this but let's get real. If you took a survey
of what is really out there you would see a lot of tower systems overloaded
according to Rohn. And as for the "wire" effect, it won't have the whole antenna
attached. Booms break, elements break and masts bend.
Everyone has to assess their own situation. I am in a 110 mph zone and I have
PE
certification for 14.8 sq.ft. of antenna on Rohn 25G, guyed at 30 - 60 - 90 ft
with 1/4" EHS. However, I will never see 110 mph winds until a strong hurricane
hits West Palm Beach directly. The highest winds we see are 50 - 60 mph bursts
during rain storms. Do I spend 1000's of dollars to plan for a wind storm that
hits every 25 years, or do I put up what I know will survive 99.9% of the winds
I
have now. As someone else said, you have insurance to pay for the other .1% of
the time. Those of you that live in 70 mph zones also get tornados more often
than I get hurricanes. Do you or can you design for a tornado. I don't think
so.
I know many big name DXers and Contesters with antenna systems that would make
Rohn have nightmares. For example, I helped a well known DXer in Atlanta put a
3
element Telrex 40 meter beam at the top of 130' of 25G. I won't go into a long
list, but I have put up and taken down 100's of towers in the past 30 years and
25G is strong stuff. Just don't go more than 30 ft. between guy points and only
use Rohn hardware.
Rohn has to meet building codes, but they also have to worry about liability of
their product. Their numbers are VERY conservative.
Before you guys start flaming me, take a look at what is out there and ask how
well it survives the wind. And please don't waist time telling me about all
the
towers that meet the specs. They are there too and if I had the money I would
only put up 55G.
Furthermore, how many of you put up used tower against Rohn advice??
73, Vant K4LM - Still putting them up and taking them down at 53.
I've done 5 this year so far, with no failures in
30yrs
Tower2sell@aol.com wrote:
> In a message dated 10/5/1999 8:43:11 PM Central Daylight Time,
> K4LM@worldnet.att.net writes:
>
> > BTW, for the guy in NC who has 75 feet of 25G guyed every 25 feet. You
> > can put almost anything you want on it. Rohn specs are at least 2:1
> > safety factory, probably 2.5:1. The antenna will go away long before
> > the tower unless a tree falls on the guy wires ( that one always bothers
> > me).
>
> Steve is most likely correct, but the allowable loads specified by ROHN are
> the maximum allowed by the building codes for the wind speed specified. The
> building codes specify minimum design strength and wind speed for the
> protection of life. This means it prudent to use a higher than minimum wind
> speed if you care about survival of your antenna tower.
>
> Second, the antenna is connected by a wire that will keep the antenna
> "catching wind" like a sail after it fails. This is why building codes do not
> allow the concept of break away antenas similar to signs.
>
> Tower2sell@aol.com
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