OpenEar: An Easy to Use Windows TETRA Voice Decoder

A new TETRA voice decoder called "OpenEar" has just been released. The program is a standalone Windows app that directly connects to an RTL-SDR. Decoding a TETRA voice signal is as simple as opening the program, tuning to the TETRA frequency and clicking on the signal. With good signal strength voice comes through very clearly. CPU usage on our PC is also minimal. 

The program source is currently not available as the author notes that he only intends to release it as open source in the future once the project is completed, and right now this is only the first early release. Right now the program is just an .exe with a few .dlls. You'll need to first install the Microsoft Visual C++ Redistributable Package linked in the Git readme. Just in case, we virus scanned the exe and tested the program in Sandboxie. It appears to be clean, and it works as intended.

In the future the author hopes to support many more protocols such as DMR, MPT1327, ACARS, AIR, GSM and more. In order to support his work he is asking for Bitcoin donations, and the donations link can be found on the Git readme.

UPDATE 1: If you're getting missing dll errors and you already installed the Visual C++ Redistributable, try downloading the missing dll's from There should only be about 5 missing.

UPDATE 2: As pointed out in the comments by Steve M. from Osmocom, this software may be in violation of several GPL licences as no source code has been released and it appears to rely on GPL code and libraries. Please take this into account.

UPDATE 3: As per update 2, the author has decided to temporarily disable the TETRA functionality pending a rewrite of the code that he will complete within one to two months). Instead he has added DMR decoding.

OpenEar TETRA Voice Decoder Screenshot
OpenEar TETRA Voice Decoder Screenshot


  1. Anonymous

    Hopefully frequency field gets more decimal places, now it has three … you can enter e.g. 434.562 but not 434.5625.

  2. moneriomaa

    one people on forum said that with avast virus scanning, received “idp.ares.generic virus detected”
    i searched and find this link about some reason for this mistake on detection
    maybe useful for some one that use AVG and Avast antivirus software.

  3. landry telliez


    I just tested the pocsag in the 466Mhz awesome reception 512 Bits on the other hand I realized that the frequencies of the firefighters are at 1200 Bits and the function is not activated a solution will be found for the 1200 Bits ???

    • moneriomaa

      it must works for pocsag 512,1200 and 2400 bits, did you test for 1200 Bits and no detection?
      i tested it for multi bitrate and messages detected, you can help for better improvement with recording I/Q
      by sdrsharp and give it to me for further review

  4. Ronen

    The Software is only for 64 bit it would be nice to have a 32 bit version
    also a PPM frequency compensation parameter for the dongle would help to tune to the correct frequency

  5. moneriomaa

    its depends that which organisation used tetra, anyway using tetra with encryption is a more power consumption for handheld unit, Anyway, I haven’t taken the time to review it yet, but it’s an interesting subject to consider in the future, although it may seem a bit difficult to get to

    • moneriomaa

      its depends that which organisation used tetra, anyway using tetra with encryption is a more power consumption for handheld unit, Anyway, I haven’t taken the time to review it yet, but it’s an interesting subject to consider in the future, although it may seem a bit difficult to get to

      • vselic

        police, road services and other public services based on law&order… it’s a shame that even single burst can’t be heard. I believe it’s most likely the same all over Europe. Hacking the traffic is illegal anyway, but if somebody just “catch” the traffic, demodulate it and than bypass the encryption in smoe way, it should not be illegal – shure – if you do not share the data with public. I belive it already exists, but for private or. government purposes, so it’s not reachable for public online.

        • Anonymous

          Even listen to such freq is illegal to in the most european Country.
          Depend where you are life there are here 3 different Tetra systems:
          380 – 400mhz
          1) Police, Fire,… -> encrypt
          2) “other” Customer -> may not encrypt
          other freq:
          3) often not encrypt

          • vselic

            Not true… if you “catch” the traffic, which is on air – which you can hear with any radio reciever (rtl sdr, mobile station etc.), it is not illegal! What you do with the captured traffic is your bussines. You haven’t stolen anything, which is on air. So if you get modulated encrypted traffic, demodulate and decrpyt it, it’s your thing – but it’s illegal, that you share traffic with public.

            Other thing would be, if you hack the base stations, steal mobile stations, disturb the traffic and so on.

  6. landry telliez

    Hello everyone I have a quick question how should I proceed to have the audio of my DMR communications I don’t receive anything?


    • moneriomaa

      i will soon add the invert (DMR-) option maybe it help you, of course this is the standard implemented version on ETSI that mostly used by Motorola, maybe other manufacture change some implementation especially on vocoder , With all these explanations you should be able to mess up the sound with a encryption or change in the vocoder or even see the “sync” word on software. non of them?!

  7. moneriomaa

    Hi all
    i try to answer all comment but some times my post sent but not shown i don’t now why!
    about performance of Tetra in previous release that i disabled it temporarily (its hard to say for me after six months of day-night trying to make c++ class for Tetra) yes some improvements (on affect of center frequncy and snr) in demodulator for reach better performance, is in my job and release it on next two months.
    about error that you get on start point of running, i compiled it with static option, for remove needs to msvcr dlls but if any other error happened, it’s maybe about systems, so reason maybe different then solution is different.
    I will decide on adding protocols after the current phases and the protocol most likely to be in the comments will probably be chosen

  8. GiamMa-based researchers

    Nice, it works in TETRA under certain conditions but with different anomalies.
    It is still a good job if not excellent!
    Today we try the DMR.
    Someone asks if there are similar decoders for POCSAG / FLEX, the answer is yes, just search online…

    • moneriomaa

      you’re welcome
      i try to reach better performance by replacement of demodulator (improvement of output for input center frequency and snr) and other improvement on next release
      for pocsag / flex and tetrapol and other protocols after current phases, i decide to new plan

    • moneriomaa

      three days before, there is no tetra version of openear
      please be patient for 1 or 2 months for new version that much better of previous version

          • RF Guy

            yes, please try it so hard as you can…There are no working Tetrapol decoder for voice, you are a GENIUS when you can make a Decoder for Windows..

            • moneriomaa

              After 10 years of experience in comint, these things have become a personal favorite for me, and I do my best to add more protocols. thanks a lot, Everyone is GENIUS and just have to believe it 😉

  9. Anto

    After put mscvr120d.dll into the same folder then it’s works flawlessly receiving tetra TMO (OS windows 7 SP 1 64bit). Still further works to be done to distinguished between 4 time slot to listen. Hopefully it can be done for future release (with auto or manual choice among 4 time slot) and put other decoder such as P25 Phase 1 and DMR.

    • moneriomaa

      As I understood this error can have many causes
      For example:
      -Your operating system should be x64 for this software
      -check compatibility option on properties
      -run as administrator
      and some other solutions that you can easyly find on youtube by searching this error

  10. Steve Markgraf

    I don’t see what’s “Open” about this. There is no published source code for this program, thus it violates the GPL of librtlsdr and the AGPL of osmo-tetra.

    The readme states:
    “4- Convert all code in Tetra protcol on osmocom tetra to c++ objective code.It is a complete conversion from the I/Q acquisition stage to Voice and other data decoded by osmocom-tetra (more than 5000 lines of code only for tetra have been rewritten for better performance and objective usage features)”

    Of course you can not simply “rewrite” code so that you can publish it under a different license, this would require blackbox-reverse engineering.

    • moneriomaa

      the Open word i used for three reason, no limitation of protocols, no limitation for use and finally open source (with condition)
      if i set osmocom-tetra on my read me this is not meant that i use exactly that, i said rewrite coz it rewrited in 6 month of time,
      software is not one part that named tetra, it have more modules and parts that currently i cant realese the code as opensource with any licence.
      i think only way that i correct my readme file for pereventing make mistake

    • moneriomaa

      “Not working?!”
      how i can take screenshot when not working?!
      or maybe you must describe your problem

      “lots to be done” yes i agree with this

    • moneriomaa

      “Not working” !?
      How i can take screenshot, if it is not working?!
      or maybe better that you describe your problem more

    • Scanner

      msvcrt120d.dll is a “debug”-version of the file msvcrt120.dll
      Release versions should not make use of debug dll files

  11. walid

    the program asked for MSVCR120D.dll in order to start , after I installed the MSVCR120D.dlle , the program will not start
    any help please

    • Chris

      I tested this decoder with my main computer, got that error massage with the missing msvcr120d.dll. After I replaced that dll, I got the same problem you get. I tried a different computer and then it worked just fine.
      It works, but under specific circumstances. Sadly, I don’t know why it doesn’t start on some computers.

      • moneriomaa

        i compiled it with static link library again and uploaded it, download openear again and try to run, tell me result thanks

    • moneriomaa

      I tried tetrapol decoding but couldn’t get the clear sound so I’m waiting for the desired sound output then to use it in this software

  12. Remon

    I think it still needs a lot of work but no mention in readme:

    Tetra has 4 time slots, nothing in the GUI.
    DMO support?
    External audio support?

    • moneriomaa

      Yes there is a lot more work to be done to make it more desirable, but it will be done gradually.

      1-for multiple slots, currently last call-id selected and send to vocoder but coz code is objective in future 4 vocoder path is replaced and can listen to all 4 slot voice.
      2-about DMO support: answer is no
      3-for external audio:
      This request has two parts
      his request has two parts
      The simplest part is to add the reading data from the audio device where this is applicable
      The second part, this protocol is pi/4DQPSK the input data must be raw(I/Q) and may be slightly different with the standard audio rate for specified demodulator that i used
      I’m trying to find a better demodulator that has a lower error rate for improve performance for weaker signal. After finding this demodulator I will definitely add a feature that is not too far off, maybe in the 3 month period.

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