This loop was built to get some DX from the SE and NW. Some mods were done to an antenna devised by L.Cebik W4RNL. My attempt was to get a "Quiet Antenna," with a low take-off angle, a 50-100 OHM impedance and something structurally sound.
Most of you know that a square loop is 90-100 OHM impedance, the largest capture area gives you the most gain. Ex: Circle best, Square next, Rectangle lower, Triangle worst. Each has a bearing on your impedance.
I chose the 24" x 12" VOVPL. The term VOVPL - stands for Vertical Oriented Vertical Polarized Loop. I stay away from the Horizontal Oriented as hams call them "Cloud Burner", good for melting snow and for keeping earthworms warm. This comment can start a good discussion.
The corner Feed provided about 75 OHMs impedance. The centre of the vertical side about 50 OHMs and the centre of the bottom (horiz) side about 100 OHMS. Note X on Diagram.
Corner feed was chosen because I could tie the 75 OHM coax to the guy rope. I did not like the centre vert or the centre horiz as it is unstable. Besides the corned feed gives you a vertical and horizontal polarization.
Most formula's call for Circ' = 1005/ Freq (Mhz). I have had good results with 1023. Also it is easier to cut than to add wire. See the diagram on above. Corner feed with 75 OHM coax is good because you can tape or tyrap it to the rope and tower. But there is always a BUT. It is only a one band antenna (20m). A multiband antenna was wanted - so twinleaf was used (not 300 OHM).
You know the black twin lead that Sask-tel uses for telephone service to your house - it is 90 Ohm twin lead. Now they are installing Fibre Optic line and for a contribution to their coffee fund the service centre will you you some. But - another BUT, you have to stand if off from anything metal (tower, eaves troughs, etc). I canvassed my neighbours for broom handles (wood) or broken hockey sticks.
Drilled a hole at the end and tyrapped twin lead - in to it, then tyrapped broomstick to tower. With a tuner it loads easily on 20, 17, 15, 12 and 10. With coax feed SWR was between 1.2 and 1.7. We like the antenna, my YL uses it to talk to the U.S.A girls on the YLRL Tangle Net. Mine is broad site to Florida, Caribbean and South America and in the other direction to Alaska, Korea and Japan. Signals are good and the noise cancelling effect of a loop helps. At my age I am downsizing, no more beams, just wire loops, who cares if I can't rotate it.
Thanks to Lloyd Cebik for the idea and the man at RARA fleamart who wanted me to write more articles.
In using coax, use an inverted drip loop to avoid water ingress and centre conductor goes to Vertical part of loop and shield to Horiz part.
73 Harv VE5AC