Nice work. And very cool concept, making your own feedhorns.
Looking through my dummy LNBFs, I found a two-horn DishNet, and two single-horn DirecTV units.
All three came out of scrapped display hardware removed from RadioShack stores some years back.
They are plastic shells, with empty die-cast metal lnb bodies inside.
In both designs, I noticed the hole in the feedhorn tube is larger than the LNB (or the 105 feed tube).
Wonder if that's a problem?
It would be if one were to try to graft any part of -my- 105 feed tube to the bigger horn.
I noticed my Dish dual bird LNB casting had two screw-on horns, just as you described.
Being dummies, they had a place for the diagonal plastic insert, but nothing there.
(that would make them receive circular, if installed)
The DirecTV single LNBs have a little cast-in step inside the tube.
That serves the same purpose - it makes the LNB work on circular.
I think I can bore that out without any trouble.
So we cut out the tubes and flange area from the legacy quad.
We turned them down on at lathe and drilled the matching holes.
Anyway, I didn't see any close-ups of the machined base of the feedhorn/tube, where it mounts to the LNB.
If I can make any out of my parts, I'll try to post 'em to encourage the next guy.
Anyway, thanks to everyone for a very educational thread. - :up