On 3/13/15 1:42 PM, Grant Saviers wrote:
Lawson "Yagi Antenna Design" page 7-12 computes the equivalent radius
of a boom to element plate as =width/4. So if you make the center
element as long as the plate and width/2 diameter, the modeling should
be close. He also states "element length should be increased 6 percent
of boom diameter" when they are electrically connected. Both are pretty
small effects for HF antennas, but if you are doing modeling, why not
include it?
This is very close to the guideline for modeling flat surfaces in NEC
using wires: make the wire diameter such that the circumference of the
wire is the spacing of the wires.
Wire diameter (particularly near the feedpoint or center of a resonant
element) doesn't have a strong effect on the EM properties. It's all
about the current there, and whether the current is spread out or not,
it generates the same field at a few meters away.
Where it would start to make a difference is if you have very closely
spaced elements (so the mutual coupling of the segments is high). If
you were modeling something like a gamma match, the physical
configuration gets important.
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