Definition
Middle frequency (MF) is the band of radio frequencies from 300 kHz to 3,000 kHz (3 MHz). In aviation, this band is used primarily for non-directional beacons (NDBs) and some long-range navigation and communication services.
Plain English
MF is a specific slice of the radio spectrum used by certain aviation navigation aids, especially older-style beacons that point an aircraft toward a ground station.
Context Anchor
Seen in aviation acronym lists, radio navigation discussions, equipment descriptions, and frequency-range references.
Derivation
From Latin medius (‘middle’) and frequentia (‘frequency,’ how often something repeats). The name simply marks this band as sitting between the low-frequency (LF) and high-frequency (HF) ranges on the radio spectrum.
Why Pilots Care
Certain navigation beacons still operate here, allowing direction-finding receivers to point toward them even when other signals are unavailable.
Intuition Check
MF does not mean any frequency that feels “middle” in everyday speech. It names a defined radio band: 300 to 3,000 kilohertz.
Example Sentence 1
The NDB transmits in the middle frequency band, so the pilot tuned the ADF receiver to its published frequency.
Example Sentence 2
Some enroute weather information is still broadcast on MF for aircraft without newer radios.