Hi,
As a data point regarding de-rating crank-up towers as a function of wind
speed and mast height, here's the results of the calculations I did on my
U.S. Tower HDX-589 based on the professional engineer's furnished
calculations. In other words, I used his calculations and varied the wind
speed and mast height for the tower fully extended (89 feet).
For a two-inch diameter mast with the antenna mounted 1 foot above the tower:
Maximum allowable antenna area at 60 mph is 79% of that at 50 mph
Maximum allowable antenna area at 70 mph is 47.5% of that at 50 mph
Tower is unable to support itself (no antenna) above 82 mph
For a two-inch diameter mast:
Maximum allowable antenna area at 11 feet above the tower (100 feet) is 75%
of that at 1 foot above the tower (90 feet).
Hope this helps give a feeling of the degree of de-rating.
73 de Bruce, WA7BNM (bhorn@hornucopia.com)
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search
|