A little OT for this group, but I figure you guys are the experts!

I've got a boat, it has an VHF FM Car Radio with a car aerial. The first
problem is that there is no ground plane, the boat is GRP. It is also lying
horizontally, it is too long to be vertical.

I want to replace the aerial something a bit more suitable. Modern cars seem
to have much shorter aerials, so is there a coil involved?

Any suggestions on making or buying a replacement?

BTW, the radio has a DIN antenna socket, so 150 Ohms I think?

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Nigel M
G1NDM (a long time ago)