car radios just seem to be more powerful than most other radios, don't know if it's the outside antenna or what it is. But be aware on most other radios, the AM antenna is built right into the receiver and i'm guessing you're going to get a ton of bleedover on the 540 frequency from WIBW (AM 580).
Case in point for myself, I can get KFAB (AM 1110) loud and clear on my car radio and on every radio that I have in the house, no matter how I rotate the radio to get good reception, I get a ton of bleedover from WHO & KWKY.