Decoding P25 Digital Trunking signals with RTL-SDR dongles and Linux

Most law enforcement agencies have moved off VHF/UHF frequencies in favor of digital trunked radio systems. Many radio scanners are unable to receive or tune to these digital trunking frequencies and scanners that can are often expensive. With about $300 you can buy an entry level digital trunking scanner off of Amazon, however, why buy something that you can ‘make’ yourself? This guide will walk you through the steps.


What You Will Need


Before we get started, there are several hardware requirements that you will need for an optimal setup. Some items are ‘optional’, in the sense that the setup will still ‘work’, but may perform poorly. Other items are required.

  • At least two RTL-SDR dongles (One monitors the control frequency, one tunes to the voice frequency)
  • Two antennas that are tunable to 800Mhz such as these. (Strong signals may resonate on antennas tuned for other frequencies but for optimal performance, seek a 800Mhz antenna or one with an 800Mhz element like a discone)
  • Debian or Ubuntu based Linux. I use a Debian based Linux Mint distribution.
  • Coffee

The overall setup can be taxing on CPU resources so you would do best to avoid attempting setup on a RaspberryPi or other similar devices.

As with all of my tutorials, I assume you already possess a basic understanding of Linux, enough so that you feel comfortable accessing the command line terminal, typing in or copy/pasting commands, and using in-terminal editors such as nano.


Installing Prerequisite Packages


Tutorial coming soon!