Building the bicircle

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.

Frequency	b/g Chnl 1 b/g Chnl 2 b/g Chnl 3 b/g Chnl 4 b/g Chnl 5 b/g Chnl 6 b/g Chnl 7 b/g Chnl 8 b/g Chnl 9 b/g Chnl 10 b/g Chnl 11 b/g Chnl 12 b/g Chnl 13 b/g Chnl 14 -NZ Indoor- a Chnl 34 a Chnl 36 a Chnl 38 a Chnl 40 a Chnl 42 (mid-range) a Chnl 44 a Chnl 46 a Chnl 48 -NZ outdoor low- a Chnl 50 a Chnl 52 a Chnl 56 a Chnl 57 (mid-range) a Chnl 58 a Chnl 60 a Chnl 64 -NZ Outdoor High- a Chnl 149 a Chnl 152 a Chnl 153 a Chnl 157 (mid-range) a Chnl 160 a Chnl 161 a Chnl 165	GHz
Free Space Wavelength		mm
Offset from reflector		mm
Reflector height		mm (Minimum)
Reflector Width		mm (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

• I originally used 3.2mm (1/8") Mang-Bronze welding rods. These are really hard to bend and I have since built these antenna with bits of broken toy railway track, and also with 2mm copper wire (strands from a discarded offcut of 16mm power cable). All worked equally as well, so my suggestion would be to use the copper wire, as it is by far the easiest to work with.
• The N-Socket is bolted to the back plate (cut from an old copper water tank) with nylon screws (I now use pop rivets).
• The antenna is held off of the back plate (1/8 wavelength) by 2mm diameter copper wire (the original plan had coax, but I see no difference in performance). From experimentation, the wires should about 1mm to 2mm apart.
• You will notice the use of nylon mounting nuts, so as not to have metal bolts above the backing plate surface. We now just use 3mm rivets, and file the bulk of the top off, after it is in place. Again, it hasn't really affected the antenna performance. It might well be doing odd things to the impedence.

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)