Many of these older cars have an inop power antenna. In my case the original antenna had been replaced by a repulsive made-in-China black whip antenna by the PO.

The original Hirschmann antennas for the pre-85 126's aren't available and the closest fit power antennas are quite expensive, IMHO.

I found a guy on E-Bay selling replacement MANUAL telescopic Hirschmann antennas for Porsches and older Benzs. They fit the 21mm hole in the 300D and 300SD's perfectly and cost under $20.

Replacement took about 10 mins (including searching for the correct wrench) and the replacement looks completely in keeping with the vehicle.

Of course the up/down button won't work any longer but you can always use your imagination