Radio navigation beacons identify themselves in Morse code, and pilots are expected to check that identifier before trusting the beacon. The FAA's Aeronautical Information Manual is blunt about it: the only positive way to identify a VOR is by its Morse code identification, or by the recorded voice identification that some stations add.
Why Morse, not voice?
VORs and NDBs are unattended ground stations. Each one keys a short identifier in Morse on top of its navigation signal; on a VOR the identifier is a 1020 Hz tone sent at about 7 words per minute. The advantages over voice:
- It fits alongside the navigation signal without disturbing it.
- It survives noise that would garble speech.
- It is language-independent: a pilot from any country can read the letters.
Some VORs alternate a recorded voice announcement ("AIRVILLE VOR", in the FAA's example) with the Morse; the Morse is still there.
What pilots actually do
- Tune the VOR or NDB frequency.
- Listen for the identifier in the audio.
- Compare it with the chart. On FAA VFR charts, each beacon's box shows its frequency, identifier and Morse code.
- If they match, the beacon is identified. Some receivers decode the identifier and display it for checking against the chart.
- If the identifier is missing, or the station is sending - . ... - (T-E-S-T), it may be under maintenance and should not be used. The FAA manual notes that during maintenance a facility may radiate a T-E-S-T code or have its code removed.
Examples
A VOR identifier is typically three letters. The VOR at John F. Kennedy International Airport is JFK:
.--- ..-. -.-
An ILS localizer adds a prefix: its identifier is three letters preceded by I (..), so a pilot can tell it from a VOR by ear. NDBs use one-, two- or three-letter identifiers.
Type any three-letter identifier into the translator and set the speed to 10 WPM (its slowest) to hear something close to what comes through the headset.
What it sounds like in the cockpit
About 7 WPM is much slower than conversational amateur CW, and that suits the job: the pilot only has to recognise three letters they already have in front of them on the chart, not copy a message. The patterns quickly become familiar shapes rather than letters to decode.
NDB (Non-Directional Beacon)
NDBs are older than VORs and transmit on low and medium frequencies, keyed with a Morse identifier on a 400 Hz or 1020 Hz tone. As satellite navigation spread, several countries began to decommission them, and the FAA has been decommissioning stand-alone NDBs in the US. They remain in use elsewhere, and the FAA's manual advises pilots using one to monitor its identification continuously.
Will it stay?
For some time yet. The United States is decommissioning roughly half of its VORs as it moves to satellite-based navigation, but it is keeping a "Minimum Operational Network" of VORs as a backup for GPS outages. Those stations keep their Morse identifiers, so recognising a few slow Morse letters remains a small but real part of flying.
Frequently asked questions
Do pilots still have to learn Morse code?
To recognise it, yes; to send it, no. Pilots check a beacon's Morse identifier against the chart before relying on it, which the FAA's manual describes as the only positive way to identify a VOR (apart from a recorded voice ID, where one exists).
How fast is aviation Morse code?
About 7 words per minute for a VOR identifier, slow enough to recognise without practice at speed.
Why do navigation beacons use Morse instead of voice?
It sits alongside the navigation signal without disturbing it, it can be read through noise, it needs no person at the station, and it doesn't depend on any language.