An amateur radio transmitter is being heard across the entire dial of a broadcast receiver. The receiver is most probably suffering from:

When a radio signal is heard across the entire dial of a broadcast receiver, it indicates that the interference is bypassing the receiver's tuned circuits (the front end) entirely. The strong local RF signal is entering the audio amplifier section directly, usually via the power cord or speaker wires. Because the tuning dial only controls the RF section, changing stations has no effect on the interfering signal that is undergoing audio rectification in the audio stage. Harmonics, poor image rejection, or splatter would typically affect only specific frequencies or sections of the dial, not the entire range.