What is a stepper motor and its use in amateur radio?

Stepper motors move in steps unlike the continous motion of usual motors. With each pulse given to the stepper motor, the shaft rotates at a fixed angle. Stepper motors have multiple toothed electromagnets arranged as a stator around a central rotor which is a gear shaped piece of iron. An external driver circuit or microcontroller is used to energize the stator electromagnets. When the first electromagnet of the stator is energized, it attracts a tooth of the gear shaped rotor. It gets alligned to the next electromagnet when it is energized in sequence. Energizing electromagnets in repeated steps moves the rotor in a step wise fashion rather than a continuous rotation. In amateur radio, stepper motors are used in automatic antenna tuners and antenna rotators. In automatic antenna tuners, the stepper motor is used to move the tuning point of variable inductors and capaciators. Microcontroller for the antenna rotator allows rotation to specific angulations, both in azimuth and elevation for satellite tracking antennas. The position is displayed in the control unit for the operator to see. Software guided antenna rotation is also possible to automate the process.