Definition
A method of carrying information on a radio signal by varying the strength (amplitude) of a steady carrier wave in step with the audio or data being transmitted. The carrier's frequency stays constant; only its size changes to encode the signal.
Plain English
A way of sending voice or sound over the radio by making the radio wave stronger and weaker to match the sound. The wave stays at the same pitch, but its size goes up and down to carry the message.
Context Anchor
Seen in aircraft radio communication discussions, especially when describing how aviation voice radios transmit and receive speech.
Derivation
Amplitude comes from the Latin amplitudo, meaning 'wide' or 'large' — it refers to the size of a wave. Modulation comes from the Latin modulari, 'to measure or regulate.' Put together: regulating the size of the wave to carry information.
Why Pilots Care
Aircraft radios rely on this method for voice communications; understanding it helps diagnose weak signals or interference during flight.
Analogy
Think of a steady light being made brighter and dimmer in the rhythm of a spoken message. The light is still the same light, but its strength changes to carry the pattern.
Intuition Check
Amplitude modulation does not mean the radio’s frequency is being changed to carry the message. In amplitude modulation, the signal strength changes while the frequency stays essentially the same.
Example Sentence 1
Aviation VHF voice communication uses amplitude modulation, so if two stations transmit on the same frequency at the same time, you'll hear a heterodyne squeal instead of one clear voice.
Example Sentence 2
Heavy static can distort amplitude modulation signals, making it harder to understand ATC instructions.