I tune between stations on the AM band when I drive around looking. Of course,
holding a SW portable out the window works, too, and allows getting out and
confirming the source. You'll note that the noise tends to rise and fall along
the lines due to, I believe, harmonics.

If the noise is internittent, check out the pole transformers and street
lights.

I don't like my Ford for the same reason. I believe Chrysler is the only one
that fully bonds everything without special order. At least they used to. Else,
ask for the police bonding package.

Bill, K5BY