Definition
A form of radio interference in which the modulation (the audio or signal information) from an unwanted transmitter is impressed onto the carrier wave of the desired transmitter, causing the unwanted signal to be heard along with, or instead of, the intended one.
Plain English
When two radio signals meet inside a receiver and one bleeds its sound onto the other, so you end up hearing a station you weren't tuned to mixed in with the one you were.
Context Anchor
Seen in radio and avionics troubleshooting, especially when a receiver is near a strong transmitter or when communication audio sounds mixed, distorted, or not tied to the selected frequency.
Derivation
From 'cross,' meaning to pass over or interfere with, and 'modulation,' the process of imposing a signal onto a carrier wave. Together: one signal's information crossing over onto another's carrier.
Why Pilots Care
It can garble ATC instructions or distort navigation signals, reducing situational awareness and increasing workload.
Analogy
It is like trying to listen to one person on a phone call while a much louder voice bleeds into the line. The call is still there, but the extra voice makes the message harder to trust.
Intuition Check
Cross modulation does not mean two aircraft intentionally using the same frequency. It means one strong radio signal is unintentionally disturbing another signal inside the receiving equipment.
Example Sentence 1
While flying near a high-power broadcast tower, the pilot heard a music station bleeding through the tower frequency, a classic case of cross modulation.
Example Sentence 2
Installing a sharper front-end filter removed the cross modulation that had been mixing tower transmissions with distant ATIS broadcasts.