The fin on top of a car is called a shark fin antenna. It handles a surprising amount of tech, including the radio, GPS, ...

I installed a new AGM battery in my 1999 Nissan Maxima. The radio will sometimes get loud and then return to normal.

If your car radio is showing no signal or no service for a station you usually receive, this could be down to one of the following things: DAB Transmitter Fault.