In signal processing, cross-modulation is a condition that occurs when one signal modulates another.
Cross modulation interference occurs when amplitude modulation (AM) from a strong undesired signal is transferred to a weaker desired signal. To test that interference has occurred, receivers usually have the undesired signal set to 1,000 μVEMF and a 20-kHz spacing between the desired and undesired signals. A 3-kHz IF filter bandwidth is usually used on the receiver. The unwanted AM signal is modulated by the desired signal with an amplitude of 20 kHz away. The undesired signal is then increased until the undesired output of 20 dB less than the desired signal is produced.