Definition
The process of recovering the original information signal (such as voice or data) from a modulated radio carrier wave. Demodulation is performed by a receiver and is the reverse of modulation, which was used at the transmitter to impress the information onto the carrier.
Plain English
It is how a radio receiver pulls the voice or data back out of the radio wave that carried it, so you hear the message instead of just the wave.
Context Anchor
Seen in discussions of aircraft radios, navigation receivers, and electronic systems that receive transmitted signals.
Derivation
From the Latin 'de-' meaning 'reverse' or 'undo,' combined with 'modulation,' which comes from the Latin 'modulari,' meaning 'to measure or regulate.' So demodulation literally means 'undoing the modulation' — reversing the process that placed the information onto the carrier wave in the first place.
Why Pilots Care
Allows pilots to receive clear voice communications and accurate navigation information from ground stations.
Analogy
It is like opening an envelope. The carrier wave is the envelope, and demodulation is the receiver opening it to get the message inside.
Intuition Check
Demodulation does not mean making a weak signal stronger. It means extracting the information that was carried by the radio wave.
Example Sentence 1
After the carrier wave reaches the aircraft's COM radio, demodulation extracts the controller's voice so the pilot can hear the clearance.
Example Sentence 2
During an ILS approach, demodulation extracts the glide slope and localizer tones from the carrier frequency.