TETRAPOL decoder for SDR: what it is and how to receive it

Decode TETRAPOL with an SDR

TETRAPOL: system information and clear-call voice (receive only).

Group: Two-way radio
Start frequency: 392 MHz
In the mode list: Network info, UHF

What TETRAPOL is

TETRAPOL is a digital trunked radio system with its own air interface (GMSK, 8 kbit/s, 10 / 12.5 kHz channels, PAS 0001-2), different from TETRA. OnAir shows the network information the control channel broadcasts.

Frequencies and settings

TETRAPOL control channel (PAS 0001-2), GMSK 8 kbit/s, 10 / 12.5 kHz (not TETRA).

Start frequency	392 MHz
Tuning range of the mode table	68 to 520 MHz
Sample rate asked	250 ksps
Lowest working rate	64 ksps
Channel width	200 kHz

OnAir takes any frequency you type; the numbers above are the mode's starting point and the range its table describes. In the app the shortcut label is Network info, UHF.

What OnAir shows

D_SYSTEM_INFO: country, system, cell, location area, channel, scramble; receive only, no voice, nothing decrypted.

Limits and what it was checked with

Checked with generated signals and impairments; recordings of real signals 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.

Receiving and the law

Receiving and the law. 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. See also Legal.

Questions about TETRAPOL

Can I decode TETRAPOL 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 TETRAPOL?

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 TETRAPOL 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.

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