The FM broadcast radio, factory installed in my car and usually tuned to 88.6 MHz, gets some interference from the 5W APRS transmitter on 144.800 MHz. It sounds like if the sensitivity of the broadcast FM receiver would go down a bit temporarily: more static FM noise is heard during the APRS "brraaap". The effect is more pronounced when I'm far away from my favourite station's transmitter and the signal is already weak. When I'm in town, it's barely noticeable.
The APRS transmitter has a properly mounted antenna (hole-through-roof, 1/4 wave vertical). The broadcast radio of the Volvo V70 does not have visible external antennas - there's one painted on the left trunk window, and apparently a second one embedded within the back right light assembly.
What can I do to fix this?