Rebuilding a dual-band mobile antenna

Until few months ago in the car I used one of those ultralight dual-band magmount antennas. They come with such a long RG174 coax that all the antenna gain at UHF is lost in the cable. Day after day, closing the car door, the little coax got pulled at the plastic base and the antenna stopped working.

A direct repair was hard, because the strong magnet is firmly glued to the small base ("E") blocking access to a solder point and the antenna itself ("A") does not screw or solder to a PL259 connector.

So I decided to destroy the original base ("E") and recover the screw ("B"): cut the plastic and pull out. The other end of the screw ("B") fits into a good old banana ("C", "F"), which plugs smootly into SO239 ("D").

I am not too confident the simple contact pressure would hold the antenna at 130 km/h, so I am still looking for a way to get everything into a PL259.