Improved digital voice P25 decoding with DSDPlus

We previously posted about the DSD digital decoding software and it’s usefulness with the RTL-SDR dongle and other signal sources. Now there’s a newly released version known as DSDPlus which promises to deliver improved decoding and clearer audio of unencrypted APCO Project 25 (P25) radio signals. This program is designed to be used with your […]

Update: HackRF based SmartNet radio monitor

We previously posted about the GNURadio based scanner for SmartNet II digital radio systems. Now Luke Berndt has updated his project info and has posted samples of the decoded system audio online. It has taken a lot of futzing, but I have my HackRF recording the Washington DC’s Fire Dept radio system and making it […]

GNURadio based scanner for SmartNet II digital radio systems

Luke Berndt posted on the HackRF-dev forum: “I built a Scanner app so I could use my HackRF to listen to my local fire department. It should work for any Moto SmartNet trunking systems that uses P25 CAI for the voice channels. It is based off the gr-smartnet code and uses DSD to decode the […]

DSD block for GNU Radio

Luke Berndt from the HackRF-dev forums has posted his work to make the functionality of DSD available to GNU Radio users in the form of a GRC block. “I have been playing around a bit and found an easy way to receive and playback digital LMR. More and more of the radio systems are going […]

RTL-SDR dsd tutorial: monitoring P25 digital voice

The crew over at has posted a simple tutorial on using the RTL-SDR dongle and free SDR# and Digital Speech Decoder software (dsd) to monitor P25 digital radio voice comms. They describe, “Digital radio voice communications are becoming more commonly used in the radio spectrum. This is due to the various improvements offered over […]

Decoding P25 with SDR#, DSD, and RTLSDR

This is another illustration of the amazing utility of the RTL-SDR and SDR# software. Here proct0r links the output from SDR# to a program known as DSD. DSD is an open source command line program originally coded in C by anonymous for Linux for the purpose of decoding digital protocols via a PC soundcard.

RTL-SDR APCO Project 25 (P25) receiver

Balint Seeber has done it again! In this video he shows how to take the RTL-SDR dongle and use it in conjunction with the open source OP25 project to successfully demodulate APCO Project 25 (P25) digital radio voice communications. P25 is a term used to refer to a modulation system used by many public safety […]

APCO25 protocol encryption cracked

The APCO25 (P25) communications protocol is a form of digital radio communications technology growing in popularity in police and other public safety radio systems in the US and abroad. Many such systems are unencrypted and can be received on digital radio scanners. Others employ encryption in an effort to prevent civilian monitoring. Now researchers with […]