OnAirTwo-way radio · Experimental
Decode TETRA with an SDR
OnAir receives TETRA. TETRA base stations (ETSI EN 300 392): network code, colour code, location area, carriers, neighbour cells, services and whether encryption is used (receive only, public broadcast, nothing decrypted).
What TETRA is
TETRA is the digital trunked radio standard used by emergency services and organisations in many countries.
Frequencies and where it is used
TETRA base station broadcast (ETSI EN 300 392-2: BSCH, BNCH, AACH, MCCH), 25 kHz channels.
In OnAir the tuning shortcut is Network info, 380 - 470 MHz; you can enter any frequency your radio reaches.
What OnAir shows for TETRA
Network code, colour code, location area, carriers and duplex spacing, services, neighbour cells, whether encryption is used; scan over a span; receive only, nothing decrypted.
This receiver is built from the published specification and checked end to end on simulated signals. It has had little or no testing on real transmissions yet, so reports and recordings on Discord are welcome.
Which radio you need
This is a shortwave mode, so the radio has to tune HF. An SDRplay, Airspy HF+ or an RTL-SDR in direct-sampling mode do that directly; with a HackRF an HF upconverter or a direct-sampling receiver is the usual route. A long wire or loop antenna matters more than the radio.
Questions about TETRA
Can I decode TETRA with an RTL-SDR?
An RTL-SDR can receive HF only in direct-sampling mode, which OnAir offers in its radio settings; results depend on the antenna. SDRplay and Airspy HF+ radios are better suited.
Is it legal to receive TETRA?
In many countries it is illegal to intercept or disclose private radio communications. OnAir is a receiver: encrypted calls show up only as encrypted and are never decrypted, and voice needs a library you install yourself. Follow the law where you live.
Can I try TETRA in OnAir without a radio?
Yes. Most modes include a built-in synthetic test signal, so you can open the screen and try the controls before you own a radio.
Try it without a radio
OnAir includes built-in synthetic test signals for most modes, so you can open this screen, see the layout and try the controls before you own a radio. The Tour button walks you through the app.