Well done, Kurt.
Rohn actually uses two wind load figures on their guying diagram pages. One is
for
"flat membered loads" (the lower of the two numbers) and the other is for
"round member
loads" (the higher of the two numbers).
Looking at it this way, there are two numbers for every antenna and two numbers
for
every tower. If you are using the high number for the tower, you should also
use the
high number for the antennnas you are putting on it. If you are using the low
number
for the tower, you can use the low number for the antennas you are putting on
it. Where
we get into trouble is when we use the high number for the tower and the low
number for
the antennas . . .
So if you are given only ONE number for the antennas, which number is it? High
or low?
I will bet it is the LOW one since that is the number that makes the antenna
seem like a
smaller load on the tower and will, therefore, sell the most antennas. So, when
matching these antennas to a tower for checking the tower windload, you had
better use
the low number provided by Rohn.
This is why it is so critically important to know how the antenna manufacture
has
determined the windload of his antennas.
I am not really aware if tower makers other than Rohn give one number or two.
From what
I have read from Kurt, I would guess they supply only one number and that would
probably
be the low one, or the most conservative one, which is the appropriate one to
use with
the numbers most antenna makers provide (the low one).
Stan w7ni@teleport.com
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