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Re: [TowerTalk] Re: Trees, Mountains, 15 degrees...

To: Jim Jones <>
Subject: Re: [TowerTalk] Re: Trees, Mountains, 15 degrees...
From: Jim Lux <>
Date: Mon, 24 Jan 2005 17:34:46 -0800
List-post: <>
At 05:25 PM 1/24/2005, Jim Jones wrote:
What effect does a tall tower (100+) have on these angles? Seems to me a small change in elevation on 1 end would make a big change in angle a few miles away.

73 Jim

Pat Barthelow wrote:

Hello again Jim,
I am assuming you gave me True azimuths, not magnetic azimuths...
Your more detailed figures detail the vertical angles over the two mountains as follows:
Red Mountain: 6.5 deg vertical angle at 45 degrees azimuth
Walter Mountain 12 deg vertical angle at 91 degress azimuth

At a distance of 2.5 miles (call it 12,500 ft) a 100 ft tower is one part in 125. One degree is about 1 part in 60 (small angle approximation of sin(theta)=theta), so the tower reduces the angle about half a degree.

HFTA, included with the ARRL Antenna Book in recent editions, can plot all this stuff out and give you a better "picture" of what's going on.


See: 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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