Tagged: TETRA

Kukuruku: A new SDR client that supports RTL-SDR

A new general purpose SDR software package called “Kukuruku” has recently been released. It appears to be a Linux only based client which is based on GNURadio. The authors write that they have several interesting features which we quote below:

Network transparency. Process the data remotely and send to the client only waterfall pixels and filtered narrowband channels instead of the entire SDR baseband. With this, you can use the SDR remotely over WAN.

Multiple demodulators running at once. How the hell can this be missing?

History browsing. It happens to me all the time: I see a new station scrolling on the waterfall. Before I manage to tune to it, it disappears (or at least the callsign is over). I have 8 GB of RAM, so why can’t I store the last minute of the entire SDR baseband for future reference?

Pluggable demodulators. Why is it so much pain to add GSM, Tetra, Tetrapol and other modes to existing software? I just want to provide a binary and have the data piped to stdin.

Squelch sucks. The squelch should not care about absolute signal level, but about level relative to surrounding channels. Additionally, it should have hysteresis and a small buffer, so when it triggers, it correctly replays the beginning of the conversation. Oh, and when recording, the squelch should timestamp the parts of conversation.

Histogram. It is difficult to see clipping on the FFT output. Why don’t we have histogram of samples?

Autotune/AFC. Obvious.

Scanner. Both for automatic demodulating all peaks in the spectrum and for retuning the SDR and finding stations. Even the crappiest rtl-sdr has 2 MHz bandwidth and can retune in 50 ms. This means 1600 channels per second. Compare this with commercial scanners.

At the moment one interesting plugin for Kukuruku is the TETRA plugin. The plugin appears to use tetra-listener and TERAPOL-kit as the demodulators, and simply passes the signal data to them for decoding and audio output.

The installation instructions can be found on the user guide. So far we unfortunately haven’t been able to install and test the software due to several compilation errors occurring, so if anyone tries this out and gets it to work, please post any installation tips in the comments. 

Kukuruku running and demodulating TETRA audio with a plugin.
Kukuruku running and demodulating TETRA audio with a plugin.

A new TETRA voice and multiframe SDS decoder

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.

The first piece of software released is called TETRA Listener and is from the Brmlab hackerspace in Prague. They write that Tetra-Listener is a new program (based on osmo-tetra) that can decode unencrypted voice and data traffic. They also write that it is very easy to set up and install since it uses Vagrant, which is a system that can be used to automatically set up a VMWare or VirtualBox Virtual Machine that has everything set up and ready to go. The instructions for using the software can then be found in the readme of the main tetra-listener page on GitHub.

The second software they have written is what they believe is the world’s first open source TETRA Multiframe SDS decoder. SDS stands for short data service and is the TETRA equivalent to SMS text messages used on a GSM network. They write that their solution can assemble long multiframe SDS messages.

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.

TETRA SDS Example
TETRA SDS Example

RTL-SDR Tutorial: Listening to TETRA Radio Channels

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.

Again, we reiterate: This tutorial is not a substitute for a thorough reading of the documentation. If you have trouble setting this software up, please refer to the telive documentation first, before asking any questions. It contains a comprehensive FAQ section which solves most of the common problems. The documentation can be found directly at https://github.com/sq5bpf/telive/raw/master/telive_doc.pdf. There is also a discussion at http://forums.radioreference.com/digital-voice-decoding-software/302347-tetra-decoding.html.

Decoding and Listening to TETRA Tutorial

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.

 
A Zoomed in TETRA Signal
A Zoomed in TETRA Signal
  
TETRA Signals Zoomed Out
A Grouping of TETRA Signals Zoomed Out

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.

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