I dismantled a piece of laboratory equipment a while ago, ending up with a small box full of stepper motors. What I know about stepper motors will go on the back of a postage stamp.
However, I did wonder about the possibility of making an antenna rotator and there are certainly a few hits on Google discussing this approach, while other
focus 
on drivable camera mounts.
Such a rotator will obviously not cope with a 20m 3-element beam but could cope with maybe a mag-loop or a small 2m yagi? I gather that the heart of the system would be either a Raspberry or an Arduino?
Wonder if anyone has been down this path?
B