i feel, that an antenna mounted outside needs to be turned at the max by 90 degrees to complete the directional search. we don't have to rotate it more because, after 90 degrees the same positions repeat with sides changed. to clarify, vertical left will become vertical right later.
so i felt the antenna if positioned east-west needs max north-south that is all and it amounts 90 degrees.
thus many pot with 270 rotation can manage it. with a 1:3 ratio.
that is to say , pot rotates 270 degrees for antenna rotation of 90 deg
hope i am able to make it clear, with my limited vocabulary.
ps: i enjoy your caption regarding Experience. (nice it is)