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Most antennas have a trigger wire, a constant wire, and a ground.
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True
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In most cases, applying 12V + to the trigger wire makes the motor turn in a direction that extends the mast.
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Yes, as long as the ground wire is grounded and there is 12v to the constant wire.
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In most cases, applying 12V + to the constant wire makes the motor turn in a direction that retracts the mast.
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I don't think so. I believe that having the 12v to constant with ground wire grounded and no 12v to trigger makes the antenna go down.
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After retracting or extending the mast fully, a circuit in the antenna disconnects power to the motor.
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True
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Some antennas use 12V - for the trigger and constant signal. Using a relay will enable you to flip this to 12V +.
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Yes... from what I understand, this is typical on old Mazdas. That is having a negative trigger wire. The constant wire is still 12v +.
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So, regardless of how the source of the 12V is switched on or off (radio trigger wire, IGN or ACC switch, remote amp lead turn-on wire), any 12V signal fed to either wire will make it go up or down.
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I don't think so. Again, constant wire should have 12v and ground wire should be grounded. The trigger with 12 volts makes antenna go up. No power on trigger makes it go down.
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If there is no signal to the trigger wire, but 12V to the constant wire, it will stay down. If there is no signal to the constant wire, but 12V to the trigger wire, it will stay up.
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Don, have you actually tested this? I think if you cut power to the constant wire, the motor is disabled. No up or down happens.
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If both 12V sources are removed, it will remain in the position last in when the sources are disconnected.
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True, but again, I believe if you just remove the constant wire (or ground), it will stop the motor.
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Here's a speculation:
- The switch on the older Mercedes that allows you to 'bump' the mast up or down is a combination momentary contact/on/off that inches it down with 12V pulsed to the trigger (up) wire, or the constant (down) wire.
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I think the way the swith works is this.
Switch off: No power to constant (trigger is irrelevant)
Switch down: 12v to constant, no power to trigger.
Switch up: 12v to constant, 12v to trigger
Someone please correct me if I'm wrong.