[AndiiT]

Hi,
I too can remember both the Electric aerials and the stick on de-mister.
The electric aerials did make a hammering noise towards the end of their travel, sonmething to do with a slipping clutch/ratchet mechanism I think.

The type that I owned could be wired directly to the car radios "Aerial power" lead, if you were lucky enough to have a radio with this facility, or via a sensor board which detected current flow as the radio was switched on (or lack of it at switch off); this relied on there being two live feeds to the motor circuitry, a "direct" one to operate the motor after the radio was switched off, and the series feed to the radio via the sensing circuit.

Regards
Andrew