Bob's obviously an expert but I want to add that after ripping off my roof mount antenna I switched to a magnetic that I kept in the back of the truck. One day stuck in slow traffic on I70 I turned my radio on and found I had surprisingly good reception. I'm sure the range was limited but wanted to share that while this stuff sounds very complicated it's not when it comes to a newbie as I was. In other words, don't let the technical stuff keep you from getting one yourself.
Also you'll find a lot of tech talk when online which typically was way over my head.