Re: NEC-LIST: flat conductors

Re: NEC-LIST, flat conductors

Mr. J. L. Smith,

The equivalence of an n-sided polygon to a round wire is given in
Johnson and Jasik, "Antenna Engineering Handbook", 1984 which is from
a 1953 paper by Y.T. Lo. For a polygon with n sides and a = length of
a side their equivalent radius is (n=2 is a strip)

  n 2 3 4 5 6 8 10

eq. rad. 0.25 0.4214 0.5903 0.7563 0.9200 1.24582 1.56884
------
  a

eq. rad. 0.5 0.7305 0.8346 0.8889 0.9204 0.9535 0.9696
-------
  r0

a = length of a side of the polygon
r0 = radius of outscribed circle

Note that there is an error in Johnson and Jasik where they state that
"a" is the radius of the outscribed circle. That looks reasonable up
to n=6 which is as far as they go, but is obviously wrong when you
evaluate Lo's result for larger n. Lo says it is the side length.

We have gotten good agreement in the propagation constant on a strip
helix modeled with the Wilton, Rao, Glisson PATCH code and the
tape-helix equation versus a NEC round wire helix with this
equivalence, radius = width/4.

Jerry Burke
LLNL
Received on Tue May 05 1998 - 18:11:24 EDT