Another version of the quadrifilar helix. This one was constructed using copper (gas) tubing, of 8mm diameter (5/16"?). The mechanical properties make the use of the center supports unnecessary.

Bending the copper tubing isn't that easy, particularly if one doesn't own the right tools (like me). I invented an improvised bending tool. It's quite important to avoid deformations in the tube - it's necessary to pass the feedline through it later!

	Raw materials: 5 meters of copper 8 mm tubing (5/16").
		The two parts cut to the lengths indicated by the calculator.
	Example of the bending of the inner loop (the smaller one). Start practicing with this loop, it doesn't have to pass the feedline, so a little deformation is permitted.
		View from above. In the center, a small PC board can be seen, used to make the connections between the four tubes. Use fiberglass here! The pertinax boards don't stand the heat (literally).
	Side view of the almost terminated antenna - it's only missing the top cover.
		Another side view of the completed antenna.
	A view of the method used to fix the lower part of the loops. Using a handsaw, I made a cut, just wide enough to receive the tubing. I then fixed the tubes using cableties. It's not possible to pass the tubes after bending, and bending the afterwards seemed too risky...
		Similar to the previous image - with a better view of the ties.
	PC Board (fibreglass) prepared to receive the tube connections (top of the antenna. Note the cuts to improve strength and ease soldering
		Connections made to the PC board, and the tubes mounted. Of course the copper tubes should be soldered to the board!

---

(c) John Coppens ON6JC/LW3HAZ

mail