Your question about powering from a 12V source has also been discussed in the treaad 5v supply recommendations, but Quark-elec has not provided any good solutions.

I tried several car USB chargers. Several produced a lot of electronic/radio noise killing nearly all VHF signals making my A024 unable to receive any AIS signals. By trial and failing I eventually ended up with a 12V to 5V USB charger that worked together with the A024.