Definition
The band of radio frequencies between 300 kilohertz (kHz) and 3,000 kilohertz (3 MHz). In aviation, medium frequency is used primarily for non-directional beacons (NDBs) and automatic direction finder (ADF) navigation, as well as some long-range communications.
Plain English
A specific slice of the radio spectrum. It sits between low frequency and high frequency, and it is the band that older ground-based navigation beacons broadcast on.
Context Anchor
Seen in discussions of aircraft radio navigation, ADF equipment, non-directional beacons, and radio frequency bands.
Derivation
The label is descriptive. Radio frequencies are grouped into bands by how many wave cycles occur per second. 'Medium' simply means this band sits in the middle range — above the low-frequency band, below the high-frequency band. The boundaries (300 kHz to 3 MHz) are international standards set by the ITU.
Why Pilots Care
Medium frequency signals support non-directional beacon navigation, especially useful over water or in remote areas where VHF coverage is limited.
Intuition Check
Medium Frequency does not mean an average-quality signal or a signal of medium strength. It means a specific numbered range of radio frequencies: 300 to 3,000 kilohertz.
Example Sentence 1
The NDB at the field transmits on a medium frequency, so the pilot tuned the ADF to 350 kHz to pick it up.
Example Sentence 2
Medium frequency signals can follow the curvature of the earth, allowing reception far beyond line-of-sight range.