[TowerTalk] Yagi versus Log Periodic

[Eric Gustafson]

>From: wa4dou@excite.com
>Date: Sat, 02 Oct 1999 16:59:36 PDT
>
> Hi Eric and Gang,
>
>Eric, your point about the fallacy in my thinking between
>parasitic array and driven array is well taken. I'm sure you're
>right. I dug out some of my antenna books today and did some
>reading on the log periodic.
>
>The reason I only considered the T-6 is because my tower is a
>Rohn 25G and I live in hurricane alley. The Rohn specs. for 110
>mph call for windloading not to exceed 8.3 sq.ft. Allowing a
>little for a rotator and mast, I don't want to go much beyond 7
>sq. ft. Even then theres a possibility that the wind it could be
>subjected to may easily exceed 110 mph. Had hurricane Floyd not
>de-intensified so quickly , it could have brought us winds
>exceeding 120-130 mph. If course, hopefully in that instance the
>antenna would give its life to save the tower.

Ok, so your constraint was size.  I was just curious.

It is generally not cost effective to attempt to design for
survival of sustained hurricane force winds.  Here is why: A very
large fraction of the wind related damage from hurricanes is due
to large pieces of junk that came off of someone else's
underdesigned carport, house, trailer, roadsign, tree (even God
doesn't design for hurricane survivability), etc.  I know this
because I used to live at Ft Walton Beach FL where hurricanes are
not unheard of.  When this flying stuff gets to your antenna or
tower is has significant surface area and mass.  _AND_ it is
going 100ish MPH when it hits.  The liklihood of your system
surviving contact with any of this flying junk is zero no matter
how well designed for "wind only" survival.  These disastrous
storms are what insurance is for.

73, Eric  N7CL

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