[CQ-Contest] Inverted Vee Trigonometry

James R. Duffey JamesDuffey at comcast.net
Sun Jan 2 11:23:52 EST 2005

Sean - This may help.

For a 90 degree included angle, that is the angle of the two legs connected
to the feedpoin,  the inverted vee will have these dimensions:

         C / [ \ C 
          /  [ h\
         / A [   \

Pardon the ASCII art.

Included Angle      Hypotenuse (C)   Ground leg (A)   Height (h)
       90               1.414 (SQRT2)   1               1
      120               1.732 (SQRT3)   2               1
      105               5               4               3

These are the easy angles and corresponding leg values to remember, and were
often used on our exams before calculators became common place. These are
practical as well: there are many old barns and out buildings in the midwest
with 37.5 degree rafters.

Just scale your lengths appropriately from these values.

For arbitrary included angles, 2*theta, or heights, h, as long as the angle
between the pole and ground is 90 degrees, you can do your own calculations
using the Pythagorean theorem:

h^2 + A^2 = C^2 

or the law of cosines

A/C = sin(theta)
h/C = cos(theta)
A/h = tan(Theta)

You could also find almost any kid who is taking ninth grade math to do
these calculations as well. :^)=  Might interest him in getting a license.
After all "that there trigonometry is good for soemthing after all."

Let us know what you do for antennas. - Dr. Mergacycle KK6MC/5

James R. Duffey KK6MC/5
Cedar Crest NM 87008 DM65

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