From Scott - 2M0VSR:

https://jcoppens.com/ant/qfh/calc.en.php generates the paper template for the holes.

Quadrifilar helicoidal antenna - Javascript on-line calculator

Compared to solid core wire, it's quite easy to get it into shape, or close enough that it tunes almost smack centre in the band

I think the rods are M4/5/6 threaded rods. Just make sure the rod will go throw the stell banding holes as they are difficult to enlarge.

Think it was this that gave me the original idea: https://tf1ez.com/qfh-antenna-build/

Parts List

• - PVC Pipe (55mm, 1meter or similar)
• - Galvanised Steel Banding - Screwfix
• - 4 x Threaded Rods + Nuts + Washers (Would probably go with M4 or smaller so that you don't have to cut the banding half-way though a whole.) Amazon Amazon Amazon
• - Some Good Quality Coax. (Messi Hyperflex 5 / Ultraflex 7 for example)

Whole thing can be built for less than £20 if you shop around / scavenge a bit more.