Date: Sat, 17 Jun 2017 23:10:47 -0700
From: Kurt Andress <andresskurt@gmail.com>
To: jim.thom@telus.net
Cc: towertalk@contesting.com
Subject: [TowerTalk] Antenna & Tower Wind Load Ratings
>Jim,
>I'm so glad to hear you know everything and have it all under control!
>This means this reflector does not, and never has ever really needed me!
>I will silently back out of here, I obviously made a really big mistake
>by making my posts here, and will leave it all to you, to go out there
>and make everything right in the World for those that need that.
>73, Kurt, K7NV
## Kurt, Im not trying to be a smart ass or anything. Im still slogging
through
the 222-G, trying to understand it all...then..trying to compare 222-G to
everything
before it..including the UBC specs. Thats a tough slog. I have been
building yagis
since 1972, so I have been around the block a few times, including installing
5 towers
for myself..and aprx 6 more for other folks. I experienced ice...once. .4
inch thick.
## I understand your points completely, but how is any yagi manufacturer
supposed to
know what exact application his yagis will be used in ? Toss in heights
ranging from
say 40-200 ft, then exposure specs B-C-D. Then topographic categories
1-2-3-4-5.
Then from fastest mile wind speed..with one type of gusts....to the 3 sec gust
method.
Then return periods called class 1, with its 25 year return period, Class 2
is 50 years,
class 3 is the dreaded 100 year return. Each return period has its own
importance factor.
Ice used to be two types, glazed and rime. Now its Glazed only, no more Rime
ice. Then
the 25-50-100 year return stats for ice. Then 3 x site classifications
1-2-3 based on
importance... knock over a few bales of hay, or kill your neighbours by their
pool.
Then Seismic loads....and seismic loading + Ice. Then 6 types of soil.
## On your excellent website, under ..windloads, it compares the various
specs..except
222-G. Correct me if Im wrong but the basic YS software uses 222-C. The
Pro version
of YS does all the other specs..except 222-G ?
Under your notes section ..under windloads
http://k7nv.com/notebook/topics/windload.html
I found the following below.....which is my whole point. How the heck is any
yagi manufacturer
supposed to spec anything. Each yagi would have to have dozens and dozens
of various combos
of specs. That will confuse joe ham..esp when he then trys to compare
several brands of say a 40M yagi.
And no software exists to depict eles inclined to the wind...aka tips bending,
shedding wind..and reducing the
load on the yagi..and tower..and mast. By how much, who knows ? I suspect
a bunch.
Jim VE7RF
There is a fundamental problem with trying to use either the later EIA or UBC
spec (or similar others) for general consumption antenna design. Both of them
require a specific antenna height and/or a siting factor to develop their
loads. I doubt that antenna manufacturers are going to design all of their
antennas for every conceivable height and/or exposure with each spec. If there
is already some confusion about what to do with existing antenna figures,
adding 20 more figures per antenna is not likely to make things easier.
EIA-222-C using its zones and wind speeds, while not the most current approach,
is easy to use and provides reasonable results. It is actually quite
conservative for many of the UBC scenarios.
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