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

[Jim Lux <jimlux@earthlink.net>]

At 05:25 PM 1/24/2005, Jim Jones wrote:
> Pat
> 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. 


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