Positioning an antennae with stepper motor

[Konstantin]

Hi.
I want to build a mount for my dish antennae on a plate that would rotate to position it. I thought of using a stepper motor and since I could not see the antennae because it would go on the roof I was thinking about a way to make it easy to position to a known direction without looking at it and without using a computer to do so.
I had this idea, using 2 trimpots, one on the axis of rotation of the antennae and the other on my desk, and use a comparator or some other simple electronic device to determine the difference of voltage on the trimpots and then send pulses to turn cw/ccw to the stepper to equalize the voltages wouldnt it be like "pointing" the antenna with the trimpot on my desk? Depending on the output of the comparator pulses from a 555 would be send to the stepper controller.

If you know of a ready made device for what I am describing here please let me know.

[Al_The_Man]

You can usually pick up a positioner on ebay or other sites that conforms to the USALS standard dish positioning protocol.
Most FTA receivers have this on board.
This will position to specific coordinates for each Sat.
Al.