It consists of 140 feet of insulated wire, the first half of which (70 feet) is space wound on an insulated tube. I used glass fibre tubing which was to hand, but PVC may be used also. My tube is 1 1/2 inches in diameter and about 5 feet 6 inches long. The turns are about 0.5 inches apart. The other 70 feet of wire acts as a loading wire and slope down from the top of the coil to near ground level. The system is coax fed to the base of the coil, with the shield or braiding going to earth.
It appears to work very well, apparently giving some horizontal and vertical polarisation.
One great advantage is the system can be tuned without having to lower the mast - by pruning the loading wire to resonate on the required part of the band. Bandwidth is also good - mine is about 30 kHz either side of resonance. I found the MFJ Antenna Analyzer MFJ-259 invaluable for this project, as well as many other experimental systems. Ensuring an efficient earth system will add to the effectiveness of the aerial I still have to improve my earth system, currently it consists of two 140 ft radials and connections to some buried guys stays. Alan, G4ERZ, has a far more elaborate and efficient ground and his results prove what we all know - the ground (or earth system) is all important. He is a tremendous signal on 160 DX wise. He still gets the same band width as I do, though.
I have worked a few DX stations with it since erecting it only a short while ago, and I think it has a lot to offer, especially for those of us blessed with relatively small gardens.
If you try this idea out, please let me know how you get on with it.