Recently Marek Sebera of ITDS Consulting wrote in to let us know about two new TETRA decoders that they have released. TETRA is a trunked radio communications system that stands for “Terrestrial Trunked Radio”. It is used heavily in many parts of the world, except for the USA.
Previously we showed how unencrypted TETRA messages could be listened to using telive in our tutorial. It is good to see alternative solutions now coming out, and in the future we hope to test this new software out.
NOTE: There is now a plugin available for SDR# that will decode TETRA fairly easily. It is still in beta and misses a few features found in telive. Check it out in this post.
TETRA is a trunked radio communications system that stands for "Terrestrial Trunked Radio". It is used heavily in many parts of the world, except for the USA. Recently, a software program called Tetra Live Monitor (telive) was released on GitHub. This software can be used along with the (patched) Osmo-TETRA software to monitor and listen to unencrypted TETRA communications.
Below we show a tutorial on how to listen to TETRA communications using a RTL-SDR RTL2832U software defined radio. This tutorial is based heavily on the telive_doc.pdf file that is written by the author of telive and included in the telive git download. Please refer to that pdf file for further details on how the software works. We have modified their tutorial slightly to make it a little easier to understand. As this code is still under heavy development if you have trouble please check their PDF file for modifications to the procedures.
Most of this tutorial is performed in Linux and we assume that you have some decent Linux experience. We also assume you have some experience with the RTL-SDR dongle and have a decent antenna capable of picking up TETRA signals in your area. If you don't have a RTL-SDR dongle yet see our Buy RTL-SDR dongles page.
Note: As of October 2016 there is now a Windows port of the Telive decoding software available. This may be an option for you if you prefer to run in Windows. More information here.
First, we will need to find some TETRA signals. The easiest way to do this is to open SDR# or another program like GQRX and look for them. TETRA signals are continuously broadcasting with a bandwidth of around 25 kHz. In most European countries they can be found at 390 - 470 MHz. In some countries they may be found around 850 MHz or 915 - 933 MHz. There may be several TETRA signals grouped in close proximity to one another. See the example images below.
An example audio clip of a TETRA signal recorded in NFM mode is shown below.
Once you have found some TETRA signals, record their frequencies. Now close SDR#, or whatever software you were using and boot into Linux. In this tutorial we use a 32-bit Ubuntu 14.04 virtual machine running on VMWare Player as our Linux system. Some of the commands may vary if you are using a different system.