I am installing several Rohn towers and want to stack antennas on the towers.
Being a "good" amateur engineer, I intend to follow the specs in the Rohn
catalog. My question is about the allowable projected area that is called out
by Rohn. For example, if I were to put up 130 foot of Rohn 45G in a 90 mph area
(coastal Maine), the book says that 12.3 sq ft of projected area of round
elements is allowable (C870478R1). I assume that is at the top of the 130 foot
tower.
Now, I want to stack antennas; say one at 60 feet, one at 100 feet and one at
130 feet. How do I calculate what is the allowable sq footage? Is it as simple
as summing the moment arms (height x sq ft of each antenna compared against 130
ft x 12.3 sq ft) or is it more complicated?
For example, a 205CA specs out at 9 sq ft, I would hope that I could put at
least three of these, and 3 155CA's (5.2 feet each) on the tower, but it
doesn't look it.
((60x9)+(100x9)+(130x9)) > (130x12.3) ........... for just the 205CA's
If this is true, how can anyone stack more than 3 large antenna's per tower?
Even a 55G installation only allows 14.8 sq ft @ 130 feet.
What am I doing wrong?
Thanks in advance for your ongoing support of my antenna project. 73, Bruce
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<color><param>0000,0000,ffff</param>Bruce Makas, K1MY ex: K1MTY,
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58 Stonegate Road N9AFY, KB9US, KS9Z
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Cape Elizabeth, Maine </color>E-mail: k1my@nlis.net
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