NEC-LIST: Equivalent diameter

Hello Roy,

This subject is summarized in detail in my chapter entitled "VLF, LF and MF
Antennas", in The Handbook of Antenna Design (editors Rudge, Milne, Olver
and Knight), Peter Peregrinus on behalf of the IEE, 1983, p. 562.

Hallen, Lo and others have calculated the equivalent radius (a) of a
polynomial by the invariance of the capacity per unit length, and for a
triangle and a square tower of side length b, they calculate a equal to
0.42b and 0.59b , respectively.

Jaggard describes the application of isoperimetric inequalities to
calculate equivalent radii, a method which can be employed for structures
of any shape. Here we bound and approximate the equivalent radius aeq by
the following inequality:

        Square route of (Area/pi) < aeq < Per/2 pi

where a is the area of the tower, and Per is the perimeter. Taking the
arithemetic mean of the above bounds yields an approximation to equivalent
radius, which for the simple polyononal structures that have been analyzed
is as accurate as the more exact solution.

Jack, VE2CV

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Does anyone know how to calculate an equivalent round diameter of square or
rectangular cross-section conductors for use in NEC?

Thanks,

Roy Lewallen
Received on Mon Mar 24 1997 - 10:42:35 EST