DUBUS rotary joint for waveguide

Neil Smith G4DBN

I've been trying to work out the best way to make a polarisation changer for waveguide, and then BOOOOM! In the current DUBUS, Jose EA3HMJ comes up with a solution for rotating stacked quarter-wave sections that I hadn't thought would work. I was trying to make each stacked section rotate a fraction of the total, which is a bit hard to manufacture, also I was looking at maybe 12-16 sections, but Jose has proved that you don't need to do that, you can get away with seven and allow each section to turn up to 30 degrees, then a pin and slot engage the next one and it rotates. All inside a sleeve. KISS principle indeed.

When I clear my machining backlog, I'm going to make one for WR90, so I can use my az-el dish to listen for big-gun EME stations, but I'll use more suitable bearing material than aluminium, perhaps a shrunk-on bronze ring around each segment, and mount them in an outer stainless steel tube, with O ring seals and needle thrust bearings like Jose used.

Sadly, I won't have much machining time as I'm back to full time working as of next Wednesday, so it will go on the pile.

Neil G4DBN

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