Thanks for the reply. The car is an 89 300e by the way. The constant voltage thing would make sense, especially if you have a switch. ie. a switch could vary the output voltage but it probably wouldn't have the ability to send a burst of voltage would it. I wonder if most of the MB antennas had this ability to vary their heights and if anyone installing one of these switches could take advantage of this?

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Fronts: Focal HC130 (5 1/4 inch) Co-axials.
Rears: Nil.
Headunit: Eclipse CD3403.
Amplifier: Audison SrX5