Definition
The specific radio frequency of an unmodulated electromagnetic wave that is transmitted from a station and used to carry an audio or data signal. The audio (voice) or data signal is impressed onto this wave through modulation, and the receiver is tuned to the carrier frequency to recover the information being sent.
Plain English
The base radio frequency that a transmitter puts out. The voice or data being sent is layered onto this base wave so it can travel through the air to a receiver tuned to the same frequency.
Context Anchor
Seen in radio communication, navigation signals, and discussions of how aircraft radios send and receive information.
Derivation
From 'carrier' -- something that carries something else. The radio wave 'carries' the voice or data signal from transmitter to receiver. The wave itself contains no information until a signal is added to it.
Why Pilots Care
When you tune a comm or nav radio to a frequency (e.g., 118.3 MHz), you are tuning to the carrier frequency. If you are not on the correct carrier frequency, you cannot receive the voice or navigation signal being transmitted, even if the station is operating normally.
Intuition Check
Carrier does not mean an airline here. It means the radio wave that carries the voice or signal.
Example Sentence 1
He tuned the comm radio to the tower's carrier frequency of 118.3 MHz before keying the mic.
Example Sentence 2
The ILS localizer uses a specific carrier frequency that is modulated to provide left-right guidance.