What would cause a broadcast AM or FM radio to receive an amateur radio transmission unintentionally?

When a consumer AM or FM broadcast radio unintentionally receives an amateur radio signal, the cause is usually fundamental overload. This happens when a strong, entirely legal amateur radio signal overwhelms the front-end circuitry of a nearby receiver. Consumer electronics often lack the robust RF filtering found in specialized communications equipment. Because they cannot filter out strong signals from adjacent or nearby frequency bands, the receiver becomes overloaded and reproduces the amateur transmission. It is a common misconception to blame the amateur operator. However, if the amateur transmitter is functioning normally and not transmitting outside its band, the fault lies entirely with the poor filtering of the consumer device.