Actually, Wireless N radios operate in either the 2.4 Ghz or 5 Ghz ranges, and utilize 20 or 40 Mhz channels in those ranges. Other consumer appliances, like microwave ovens also operate in the 2.4 Ghz neighborhood. But, that's not your question.
FM/AM radios don't operate in these ranges, but I think they're close to 100Mhz, which I think the 100Mb Ethernet (FastEthernet) standard may run at. Maybe you could try replacing your current cable with a shielded Ethernet cable. It may be a problem with they physical interface leaking the frequency on the router or the printer end.