[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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