Definition
L/MF refers to the Low Frequency (30–300 kHz) and Medium Frequency (300–3,000 kHz) radio bands used by certain aviation navigation aids and broadcast services, including non-directional beacons (NDBs) and the Transcribed Weather Broadcast (TWEB) service in Alaska.
Plain English
A range of older, lower-frequency radio bands still used in aviation for some beacons and weather broadcasts, especially in Alaska.
Context Anchor
Seen in Alaska Transcribed Weather Broadcast listings and other FAA references that show which radio outlet carries a weather broadcast.
Derivation
Low Frequency and Medium Frequency are standard radio band names defined by international convention. The slash simply combines the two adjacent bands into one label because aviation services in this range often span both.
Why Pilots Care
Provided pilots in remote Alaskan areas with continuous weather information before modern systems replaced the service.
Intuition Check
Do not read L/MF as a weather type or a signal-quality rating. It identifies the radio frequency band used to send the broadcast.
Example Sentence 1
In Alaska, pilots can tune an L/MF receiver to the published frequency to hear the TWEB recording for their route.
Example Sentence 2
TWEB broadcasts on L/MF helped pilots plan flights across Alaska when no other weather source was nearby.