HFDL (aircraft data over shortwave)
A shortwave data link that lets airliners exchange messages when far from land, for example over oceans.
ModeHFDL
FamilyAviation data
Audio exampleComing
What does it sound like?
Plate 25Aviation data
Short bursts of dense digital noise, plus regular 'squitter' announcements from ground stations.
Field marksShort data bursts from aircraft and ground stationsHeard between about 2 and 22 MHz
Who uses it?
Airlines, aircraft and a worldwide network of ground stations.
Where and when can I hear it?
Many frequencies between about 2 and 22 MHz, for example 8.927 and 10.081 MHz.
What do the decoded parts mean?
- Aircraft and ground station: Which plane and which ground station are talking.
- Position reports: Where aircraft are.
Easily confused with
- ACARS (aircraft messages), from the same family
- VDL Mode 2 (aircraft data link), from the same family