[Antennaware] Equivalent Diameter of Triangular Tower

[Bill Tippett]

K9AY:

 > This is easily explained by uncertainty in choosing an equivalent 
diameter "solid wire" for
the 25G tower (I used 5 inches).

         That sounds too small.  Here's the formula I used to model 
my 160 vertical made of Rohn 45:

http://lists.contesting.com/archives//html/Antennaware/2002-05/msg00001.html

Equivalent Cylindrical Diameter = 2 * CUBEROOT [(D * F^2)/2]

where D = tube diameter and F = Face width.  For Rohn 45, D = 1.25"
and F = 18", so cylindrical diameter equivalent = 11.7446"

This turned out to be very accurate in predicting both the tap point 
and capacitance needed for my shunt fed tower (and later a 3-el 
parasitic array using the tower as the driven element).  I don't have 
the tube diameter for Rohn 25 handy to actually go through the 
formula but think the equivalent diameter might be closer to 8" (just 
mentally scaling the result above).

                                         73,  Bill  W4ZV