Gnuradio companion schematics for receiving TETRA digital radio using USRP and LIMESDR

TETRA is a digital trunk radio system widely employed by commercial organizations as well as law enforcement. Often it has been implemented without encryption, presumably since the additional license fees are expensive. For example, the TETRA network used by the municipal police in Prague, Czech Republic, is one such case, and it was actually recently publicized in country-wide newspapers ;-).

Thanks to the work of the osmocom team and recent contributions by Jacek Lipkowski who also wrote an excellent HOWTO on the topic it is now very easy to receive unencrypted TETRA using the RTL-SDR dongle - just carefully read the mentioned manual.

I have a USRP1 on my bench, connected to a HAM 70cm band antenna, so naturally I have experimented a bit trying to use USRP receiver instead of RTL-SDR for receiving TETRA. Due to the modular structure of Telive and the simplicity of the gnuradio frontend it was a matter of couple of minutes to adapt the grc blok diagram, nevertheless, I give the modified grc files for convenience below:

usrp_telive_1ch_simple_gr37_udp.grc
usrptelive_6ch_gr37_udp.grc

Recently I have crowdfunded the LIMESDR project and recently received my unit (version 1.4s). I have put the unit into a metallic unclosure and used 10 SMA/u.fl pigtails to get all RX and TX ports on the front panel. I have also attached heatsinks on the 3 big chips and on the voltage regulator to prevent overheating, during RX only operation I can now comfortably hold finger on the heatsinks. As a first easy application I have adapted the GRC script for TETRA receiving also for LIMEDR, the result being lime_telive_6ch_gr37_udp.grc.

The unix script to run the receiver is lime_telive_6ch_gr37_udp.grc, for the different hardware just the first command has to be changed.

Notice that TETRAPOL (used e.g. by Czech country police) is a completely different digital radio scheme incompatible to TETRA. Some effort towards receiving TETRAPOL has been undertaken by BRMLAB. However, almost all TETRAPOL traffic is encrypted and the algorithm is not publicly known.

See also my page about gsm


----------------



Back to my electronics page


My hobby page


My main page


TOP of my family pages