Join Date: Mar 2009
Location: Dunnville, Ontario on the Grand River, North shore Lake Erie
The aperture is needed, otherwise you'd just have a flat piece of material with no electro magnetic field reference points.
I made one with an old 4221 reflector 1'x 2' mesh:
[It looks like an old style 4221 with no wisker elements]
I modified the outside height dimensions to 28" high [for VHF-Hi range]
I modified the outside width to 20" [for optimum scatter capture]
The hole size is vertical cut into the center of the screen mesh:
4" wide x 14" tall [7" above & below the balun feed point]
Note: 16" high slot would give more range into the VHF-Hi, but at a cost to the upper UHF
Tip: I left the wire mesh stubs at the center for balun connection points.
Note: The screen mesh must not be electrically bonded to the mounting mast.
This one seems to do as well as the old 4221, but with a wider beamwidth contour and it's bi-directional.
This design pretty well serves as a 7-51 range antenna with performance similar to a 4221.
Reception RF freq sampling:
I get analog VHF 5, 6, 9, 11, 13 strong & up to analog UHF 19, 47 strong but analog 57 is weak
I get digital VHF 7.1, 12.1 & digital UHF 14.1, 50.1 all @ 100%