[TowerTalk] ridge top derating factors

[John Langdon]

Just an unscientific observation, but I am on a not very high ridge, but I
have seen the antennas on the tower (at various heights up to 195')
deflecting in two different directions from each other and both different
from what the prevailing winds were on the ground, and I have also started
up the tower in relative calm at the ground level and decided not to work
because the winds were too much at 90', and found it still calm when I got
back down to the base of the tower again. Never boring!

73 John N5CQ


-----Original Message-----
From: owner-towertalk@contesting.com
[mailto:owner-towertalk@contesting.com]On Behalf Of Bill Aycock
Sent: Thursday, April 13, 2000 3:05 PM
To: Tower Talk
Subject: Re: [TowerTalk] ridge top derating factors


Steve, etal- the opposite is also true- I am blessed to be on the flat top
of a ridge.- near the center of a flat that is about 300 yds wide, about
300 to 600 ft above valleys on both sides. (1000 ft above the Tennessee
river, to my SE)

The wind frequently come blasting out of the southwest, hits the ridge,
lifts OVER me, and comes down like a bucket of sand onto the valley to the
east. I had my neighbor lose 50-60 very large Poplar trees (way over 100
ft) , in what he thought was the "shadow" of my place, while I didnt even
get the plants on the deck tumbled. This was the inland portion of
Hurricane Opal.

On a cloudy, thunderstormy day, I can watch the clouds take this same path.
 If I (and my antennas) were in the valley, I would be in real trouble. I
think that, if I were a "big gun" and had more feet of tower, I would be,
also, but with less than 100', I am relatively protected.

Bill- W4BSG

At 11:48 AM 4/13/00 EDT, Steve wrote:
>
>     Exposed ridges are particularly exposed not only to direct horizontal
>winds but also venturi winds coming UP the side of the hill and hitting the
>antennas from underneath. This is where you'll need 120 degree trusses on
>your antenna booms to keep them from breaking.
>
>Cheers,    Steve    K7LXC
>Tower Tech
>
-
Bill Aycock   ---   Persimmon Hill
 Woodville, Alabama, US 35776
 (in the N.E. corner of the State)
      W4BSG   --   Grid EM64vr
        baycock@HiWAAY.net
             w4bsg@arrl.net

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