Building the bicircle

This is simple to make and I'm getting 14Dbi, which is the theoretical gain (comparing it to a commercial 14dbi antenna over a 3km wide valley, it gives the same gain).

I also tried different heights off of the reflector. I varied the distance from 1/8 to 1/4. It seemed to make no difference at all. It should alter the impedance. Different plate widths and heights made no obvious difference either. Nor does the shape of the circle. I had eliptical shapes and some very odd ones, but they all worked as well.

Free Space
Offset from reflectormm
Reflector heightmm (Minimum)
Reflector Widthmm (Minimum)
The size of the reflector and its distance from the active element affect the feed impedance. The ARRL handbook says there should be a 1/4 wavelength edge beyond the active element.

Misc Notes

From the front (vertically polarized). From the Back Looking down on it when it is aligned for horizontal polarization (i.e. the circles are one above the other)

This one is a test version at 3/16 of a wavelength from the reflector.

Variant with parabolic backing plate. Something we tried for long links, which worked well (toy Rail used for the circles)