From "Physical Design of Yagi Antennas," ARRL 1992, pg. 9-2:
"This problem is resolved in a short paper by Jaggard [D. Jaggard, "On
Bounding the Equivalent Radius," IEEE Trans AP, Vol. AP-28, May 1980,
pp. 384-388, https://ieeexplore.ieee.org/document/1142336] Jaggard shows
that the equivalent radius ae of a noncircular shape must lie between
the radii ai and ac of the inscribed and circumscribed circles which
geometrically bound the noncircular conductor. Further, he shows that
these bounds can be narrowed by the use of radii ain and aout which are
the radii of circles of the area A and perimeter P of the cross-section
shape of the conductor, ain = sqrt(A/pi) and aout = P/2pi. A
satisfactory estimate for the equivalent radius is the mean of the two
bounding radii."
A freely downloadable scan of my 1992 book with more details about the
equivalent radius of irregular shapes, "Physical Design of Yagi
Antennas," is at
https://www.dropbox.com/s/hmhkeofz0igrg1e/Physical%20Design%20Of%20Yagi%20Antennas%20D%20B%20Leeson%20V2.pdf?dl=0
73 de Dave, W6NL/HC8L
On 6/25/24 5:40 AM, john@kk9a.com wrote:
To check for interaction, I have done the easy model method of using
a very thick wire for the tower. Since the tower is triangular and a
wire model is round, I took a wild guess at the wire diameter. I
never thought of matching the surface area.
John KK9A
Jim Lux wrote:
There's two ways to approach the modeling. The easiest is to model a
"very thick" wire - match the surface area of the tower with the
surface area of the wire.
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