2nd attempt to send this
Hi Dick,
See if you can find a copy of
+++++++++++++++++++++++++++++++++++++++++
Physical Design of Yagi Antennas
-- by Dr. David B. Leeson, W6QHS.
Packed with information on how to design or reinforce Yagi antennas so
they can survive in the most adverse weather conditions like
120-mile-per-hour winds! Covers the structural design of elements, booms
and masts, plus the electrical design of Yagi antennas.
340 pages. First edition, © 1992, The American Radio Relay League, Inc.
(ISBN: 0-87259-381-9) #3819
This publication is out of print.
+++++++++++++++++++++++++++++++++++++++++++++++
It will tell you all (and then some) you need to know about calculating
forces due to winds and specifying masts. There's also a lot of stuff
about mechanical design of yagis that isn't really applicable to your
situation, given that you aren't designing your own antennas.
There's a lot of algebra as he goes through the process of deriving the
equations used in the calculations. You can simply ignore this and just
use the final resulting equations for your calculations.
The book refers to spreadsheets for doing various calculations. These
spreadsheets don't come with the book. They are available at
http://www.realhamradio.com/Download.htm
It doesn't say anything about how you keep a tower up or whether your
roof will stay on. It does enable you to calculate the forces which
your guying system will have to deal with or, if guys aren't involved,
the forces the tower will exert on the roof.
ARRL used to list the book at $20 but I bought a copy from HRO a couple
of weeks ago for $15, so the book seems to still be available, probably
not for long.
Another great tower resource is at http://www.qsl.net/n1lo/towers.txt
From all of this you should be able to calculate the forces your system
has to be able to withstand. However, there is nothing here which will
tell you what you have to do to to your roof to enable it to withstand
these forces.
Perhaps someone can come up with some suggestions as to how to deal with
this part.
As you will see when you get into this stuff, it is a rather large topic.
I hope this helps you to design a system that you'll be comfortable with.
73 de Jim Smith VE7FO
>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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