Definition
A long-range, voice radio communication system operating in the high frequency band (roughly 3 to 30 MHz) that uses signals reflected off the ionosphere to reach distances far beyond line-of-sight, typically used for oceanic and remote-area air traffic communications.
Plain English
A type of long-distance radio used to talk to controllers when the aircraft is too far from any ground station to use normal radios — common over oceans and remote areas.
Context Anchor
Pilots encounter High Frequency Communications on oceanic, remote-area, and long-range flights where ground radio stations may be far apart.
Derivation
High frequency' refers to the radio band of 3 to 30 MHz. These frequencies bounce off the ionosphere — a charged layer of the upper atmosphere — which lets the signal travel thousands of miles instead of being limited to line-of-sight like VHF.
Why Pilots Care
It provides the only practical voice and text contact with controllers on long over-water flights where line-of-sight radios cannot reach.
Intuition Check
High does not mean the radio is louder or stronger here. It means the radio signal is in a specific frequency range: 3 to 30 megahertz.
Example Sentence 1
Before crossing into oceanic airspace, the crew checked in with the controller on HF and gave their first position report.
Example Sentence 2
Poor conditions made high frequency communications unreadable, so the pilot requested a relay through another aircraft.