Waveguide Adaptor for Octagon LNB to 22mm

The simple approach to attach an Octagon LNB to a circular waveguide is to saw off the ridged scalar horn and push the cut end into a split 22mm pipe, but I decided to do it the long way. I made up a conical plug from brass to fit against the cone of the horn, then bored a tapered hole inside the plug to match the 17.5mm ID of the Octagon to the 20.2mm ID of 22mm water pipe waveguide. Probably totally unnecessary, but I had fun doing it.

Parts of the adaptor and mount with the 22mm waveguide and bare LNB

First step was a CAD design

CAD Model of the Octagon LNB horn and tube section
The brass adaptor plug in place
Adaptor plug and the locking ring with the O ring compression seal
Front collar in place, without locking ring
Complete assembly with 22mm copper tube inserted into the plug with collar and locking ring
Tapered end of the plug
22mm bored socket for the copper tube
Collar slid over the plug
Collar showing the thread
Collar with locking ring in place
Collar, adaptor and locking ring in place
View into the tapered bore of the adaptor
Complete assembly ready to attach the dual-band POTY feedhorn

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