I needed a lightweight mast head rotator for a fibreglass 14m mast.  All the commercially available ones are way too heavy - so what I came up with is this:

I bought (eBay) a Radio Control Yacht winch servo which moves 18 turns in response to the input from an RC set.  This was connected by a toothed belt drive to a bigger pulley on the bottom of the antenna which was just sleeved over the top section of the mast.

Instead of an RC Transmitter & receiver, I just extended the three wires from the servo to my shack and in there had a 'Servo Tester' box.  This is just a box with a knob.  When you turn the knob, the servo turns proportionally.  The knob only turns 270 degrees - so I marked a back plate 0 to 360 deg N,S,E,W over the 270 deg range.

It worked exceptionally well, was fast and accurate and probably only weighed 200g including the pulleys.  The servos are also waterproof.  If you used an ordinary servo which rotates 180 deg, similarly with pulleys & toothed belts / gears you could convert this to 360 deg.

Since then, I've moved it to the attic where I have a mag loop which is rotated by the winch servo and tuned by another servo, both connected to servo testers.

Servos these days are pretty cheap and the servo testers cost under £5 - so not an expensive option.

Si