While second type have a
simple knob used at the same time to rotate the antenna and to report its
position (such as small TV-antenna's rotator), the first one is more common for
In the first type we have basically:
circuit to move the rotator;
circuit to report antenna's position.
CIRCUIT TO MOVE THE ROTATOR
A small motor (See Fig 3)
(usually 24 V AC)
is in the body of the rotator; by some gear (See Fig 4) the speed of the
motor is reduced at about 1 turn/minute;
two switches on the control box let the rotator turn left or right, due to an dephasing elettrolitic capacitor (See Fig 5); often the capacitor take place in the control box, but in oldest type it's in the body of rotator.
A mechanical end-stroke (See Fig 6) stops the rotator at 360/450 degrees (in the expensive types there is also a microswitch);
in medium-load rotator the same gear system acts as a brake, while in high-load type there is a mechanical one.
This circuit need at least 3 wire (24 VAC + LEFT e RIGHT).
CIRCUIT FOR REPORTING ANTENNA POSITION
It's based on a bridge
made by two (variable) resistor (See Fig 7),
the one in the control box, the other in the rotator body, wich turn together
the antenna; a voltage applied to it vary with the resistor position (wich means
antenna position); this voltage is comparated with the one on the "control
box" resistor; if there are differences the bridge is unbalanced and that
make a meter to turn until the bridge is balanced (See Fig 8).
This circuit need at least 2 wire (usually 3).