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

[Jim Lux]

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.