Adapting Invacom ADF-120 feedhorn to Kathrein feed boss.

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Just as a turning exercise in the lathe I made another adaptor to match the Invacom feedhorn to the Kathrein feed boss. Since I had no alloy bar in a suitable diameter I used an old Picador 4" V-pulley for raw materials.

First I fitted the pulley in the lathe with inside jaws fitted to the 3-jaw, Burnerd chuck. Then the boring went smoothly from the 1/2" original to the desired 25mm. I used the Invacom feedhorn as a plug gauge to ensure a close fit when I came close to the correct bore. Then I matched the outside diameter of one pulley flange to the 69.5mm Ø Kathrein original. 

The image shows one side of the adapter. I also ground off the point of the hardened, grub, fixing screw and polished the new, slightly convex, contact face with emery paper. This will save marring the feedhorn throat with the clamping screw. A nylon grub screw would be much better.

The original bowl-shaped feed boss of my own Kathrein 2.2m dish has a matching hole for the original feedhorn.  The critical dimensions are identical to the triangular Kathrein feed boss shown below.

The other 2.2m Kathrein dish has an impressively massive  triangular feed boss. The impression of the skew clamping ring is clearly seen on the upper face of the feed boss. One arm holding screw has been removed for boring out to a larger diameter to take modern coaxial cable.

The skew ring clamps the 69.5mm flange on the original Kathrein feedhorns. Now it can clamp the home made adapter. Allowing the Invacom ADF-120 feedhorn to be used with a modern C-120 LNB and original Kathrein feed boss.

Because of the deeply recessed faces of the Picador cast V-pulley there wasn't enough meat to provide a 60mm seat for the Kathrein skew ring. More by good fortune, than anything else, the three fixing screws of the Kathrein skew, clamping ring will hold the adaptor perfectly central in the boss. The adapter flange is 3mm thick to match the original, Kathrein feedhorns.

While I was using the lathe I bored out the stainless steel, arm fixing screws of the other Kathrein 2.2m dish to match my own. 

This would allow the owner to run modern, high quality coaxial cable neatly inside the hollow, alloy arms. This saves clipping the cable to the outside of the feed support arms with tie-wraps and looks very much neater.

Click on any image for an enlargement.

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