Re: Feko help
Rays are only visible for UTD solutions. The PO is more like shining a torch on something and checking if it is visible. Rays can't be viewed for PO solutions.
For the UTD you have to make unmeshed plates and they have to be a minimum of 3 wavelengths long, otherwise the approximation becomes invalid.
You can try the polyline, elliptical arc, bezier curve or fitted spline. What does your loop look like?
If you want to give it finite thickness then the path sweep tool is very useful.