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TrunkSniffer is an advanced, software-based, MPT-1327 trunked radio network tracker. It all started, as usual, with a curiosity as to how my local trunked radio networks worked, grabbing a copy of the MPT-1327 standard, and slowly writing a decoder bit-by-bit (literally!). It took many hours of looking at waveforms and decoding single bits by hand to make sure the algorithms were performing as they should. The result was this:

I initially released TrunkSniffer in two versions, a software-locked one and a freely-installable that was protected by a HASP key. I can no longer maintain the software, the sales have fallen down to nothing (partly due to digital TETRA networks taking over in many countries, partly due to lack of time in effectively promoting the software), and so I’ve decided to release the software for free. You can download the installer, and the unprotected executable, at the end of the page.

TrunkSniffer was reviewed in Shortwave Magazine, and also online. Amongst its users were network operators and intelligence agencies in several countries. Some alternatives existed such as the excellent FTrunk and WinRadio with the trunking option.

What is really amazing is how much I’ve learned since then about usability and UI design, and how many things I would do differently, such as the extremely ugly ‘apply’ and ‘cancel’ buttons in the settings windows.


  • Decodes all common MPT1327 codewords, including SDMs.
  • No special hardware required, or discriminator audio. Simply feed it speaker audio from the control channel, and decoding will begin.
  • Serial port control of one or two receivers. Simultaneously track the control channel activity while you follow voice calls.
  • Voice call tracking override, to drop a current call and follow a new call (supported when using two receivers, one dedicated to control channel tracking).
  • Automatic tuning of the control channel and traffic channels. Follow group calls and individual calls.
  • Easy network management with network profiles.
  • Automatic control channel hunt, for systems that rotate the control channel over different radio channels during the day.
  • Full filtering capabilities by creating fleets within the network.
  • Logging of decoded data to disk, with dated log files.
  • Call recording to .wav or .mp3.
  • Direct control over the sound card, for mute and volume control.
  • AudioTuner tool, which helps classify control channels and configure decoding for optimum performance.
  • Password-protected telnet server, which gives remote access to decoded data in real time.
  • Fully automated launch – start the program, and it will tune your receivers and start tracking automatically. Useful for remote stations that may reboot from time to time.
  • Tracking filters can be drilled down to individual fleets and individual radios within a fleet.

Screenshots (click for full-size):

Audio Tuner – useful for getting your decoder performance as good as possible:


Audio configuration screen:

Audio configuration

Network properties – all MPT-1327 fleet numbering plans can be configured:

Network properties

Finally, the main screen, showing how to filter the different types of codewords being decoded:

Codeword filtering

You can download the installer here, extract the .zip and run Install.exe. Then, download this file, which contains a free, unlocked version, unzip it, and copy the extracted trunksniffer.exe over the existing one, usually found in C:\Program Files\TrunkSniffer. Enjoy!

Please note that this software comes with no warranties, no support, and no guarantee that it will work with your equipment or trunked network!