Definition
To vary one characteristic of a signal — such as its amplitude, frequency, or phase — in a controlled way so that it carries information. In aviation radio, modulation is how voice or data is impressed onto a radio carrier wave for transmission.
Plain English
To change something in a steady, controlled way so it can carry useful information. In radio, it means shaping a signal so your voice rides along with it.
Context Anchor
Seen in aircraft radio, navigation, and communication equipment discussions.
Derivation
From the Latin modulari, meaning 'to measure off' or 'to regulate.' The idea is controlled variation — changing something in a measured way, not randomly. That fits the radio meaning: a carrier wave is varied in a precise pattern to carry voice or data.
Why Pilots Care
Clear modulation is required for readable ATC transmissions; poor modulation produces garbled or unreadable calls that can compromise safety.
Intuition Check
Do not read modulate here as simply “turn up” or “turn down.” In aviation radio use, it means changing a signal in a controlled pattern so information can ride on it.
Example Sentence 1
The transmitter modulates the carrier wave with the pilot's voice so it can be sent to the control tower.
Example Sentence 2
The ELT modulates a swept-tone signal on 121.5 MHz to alert search aircraft.