How to complain about interference
Complaints should go to the station being interfered with, not the station(s) causing the interference. There are a few exceptions, however. If you feel that an IBOC station's own digital emissions have degraded their analog signal quality, you should let them know. Or, if you have reason to believe that their IBOC equipment is malfunctioning, you should contact them, but make sure you're on firm ground before you do so.
Keep in mind that interference complaints are more likely to be taken seriously if they affect reception in or near protected contours. You can find out what your local stations are using V-Soft's zip code radio locator.
The first question to ask yourself is whether the reception is by skywave or groundwave. Only the Class A stations on the "clear" channels have protected skywave service, so complaints about interference to skywave signals will likely fall on deaf ears unless one of those stations is on the receiving end of the interference. If in doubt, you can check a station's class using sites such as fccinfo.com or radio-locator.com. Of course, some of the large market Class A's have little or no interest in skywave service, WOR being a prime example. At the other end of the spectrum are stations such as WSM that still have big skywave audiences, and thus should be more receptive to interference reports.