First addressed in 2020, the consensus was "don't put a fuse on the negative wire to your mobile ham rig, because" eh, go read the post. Lots of good reasons given there.
However, this auto mechanic makes a valid point for having a fuse on the ground side in this video. Go and watch (7 minutes), you'll see a new side of things. Oh, here's the TLDW: Sometimes the engine ground cable ends corrode. With 100 to 150 amps cranking current, if that ground cable connection isn't pretty darned good, it's going shoot some current back through various unintended paths and ultimately through the negative/ground wire and into your radio, in which case you really really want a fuse on that thing. This is especially a problem if the antenna is permanently mounted on the car body, i.e. not a magnet mount.
I see the guy's point, and it is a valid one. He's actually seen the bad effects this can have. However because all my vehicle antennas are mag mounts, it's moot. I'll keep fusing the positive-side only, but if I change my antenna & mounting system I'll consider adding a fuse to the negative wire.
Finally, I'd previously written back in 2020:
Of course all this is moot for a fully-floating ground plane antenna, but how often do we see those in mobile installs?
Turns out, all the darned time, with every single magnet-mount antenna out there, which is something like half of the antennas actually in use.
It's surprises like this that keep the hobby fresh.
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