Richard,
I remember seeing something like your string idea. Used a
'barn-door' hinge with a rope-loop attached. Pull one rope the
antenna 'stood up', pull the other it laid down. Ran the ropes
through a couple of 'turning blocks', into the shack's window.
The 'turning blocks were low on the tower so the rope sort of
twisted around the tower when the beam was turned. Didn't seem
to be much of a bother...
'Doc