Over on YouTube Corrosive from the SignalsEverywhere channel has uploaded a new video showing us how to set up P25 trunking and decoding with DSDPlus Fastlane and only a single RTL-SDR.
Normally two dongles are required to follow a P25 trunking system. One dongle continuously receives the trunking channel, and a second tunes to the voice channel chosen by the trunking channel. However, the latest DSDPlus Fastlane has a feature that allows one only dongle to be used. It works by tuning back and forth between the control and voice channel. The disadvantage is that trunking information could be missed while tuned to a voice channel, so some calls could be missed.
RTL SDR Setup P25 Trunking With 1 SDR and DSDPlus FastLane
RadioCapture.com is a website run by Matt Mills that is capable of automatically capturing trunked radio communications from various agencies such as the emergency services and creating publicly accessible historical and live logs of the audio. This is a concept different to radio scanner streams, as all audio is logged and historical audio can be accessed easily at any time.
The system is based on SDR hardware such as the RTL-SDR. Currently Matt runs a receiver in Denver and captures Denver PD which can be listened to on the site without needing to log in. Once logged in (registration is free), other talkgroups available include various agencies in Colorado, New Jersey and Pennsylvania.
Recently Matt has put a call out for people to help support the site via Patreon. He notes that RadioCapture is currently run as a hobby, but with monetary support he hopes to be able to expand the site into a business and have receivers listening and uploading worldwide. He writes:
Hey! Thanks for supporting the continued operation and development of Radiocapture.com. This is a hobby project I've been working on this since late 2011. I'd like to turn it into a real business with your help.
Radiocapture.com is a software defined radio system I built that captures entire trunked radio systems. It demodulates and captures every call on every channel of one, or many systems.
A single RadioCapture server can capture hundreds of simultaneous voice transmissions and a bunch of sites, additionally it's designed in such a way that it can run across multiple computers. My biggest RF site uses 3 machines to capture 19 P25 systems, and easily hits more than 100 active voice channels recordings simultaneously every day.
Matt has also noted that if the site is able to become self-sustaining via Patreon, he hopes to also be able to bring out a RadioCapture kit consisting of 10-16 RTL-SDR dongles, hubs and cables which would allow anyone to easily capture and upload almost all trunked communications from their area. He also notes that at the time of writing:
RadioCapture has 701790271 unique recordings of 503779875 unique transmissions (some calls get captured on multiple transmitters) from the 21 systems that have been captured
If you're interested in talking to Matt about the site, you can also join his Rocket.Chat room at radiocapture.chat.
In his last video, Corrosive from the SignalsEverywhere YouTube channel showed us a quick guide on setting up a Phase 1 P25 digital voice decoder with two RTL-SDR dongles and the DSDPlus Fastlane decoder.
Now in his latest video Corrosive continues with the DSDPlus tutorial and this time explains how to set up priority and groups. On a trunked radio system there may be many different agencies using the same system simultaneously. Without priorities and groups, you would be listening to all communications in the system, and following a conversation within a particular agency would be difficult. Setting up priorities and groups allows you to filter out the conversations that you are not interested in, allowing you to focus on listening in to a particular agency only.
RTL SDR Digital Radio Scanning Priority and Groups With DSDPlus Fastlane Setup Tutorial
DSDPlus is a popular piece of software often used with RTL-SDR dongles to listen to unencrypted digital voice signals such as P25 and DMR. Digital voice is now commonly used by many Police and emergency services as well as business radio. DSDPlus fastlane is DSD's paid upgrade which allows subscribers to access to the latest releases of DSDPlus early.
Over on the SignalsEverywhere YouTube channel, Corrosive has uploaded a quick video guide that shows how to use DSDPlus Fastlane and two RTL-SDR dongles to set up a Phase 1 P25 voice decoder that automatically follows a P25 trunking channel. The basic process involves running two FMP instances which is a program in the DSDPlus suite that connects to the RTL-SDR's and receives the signal. One DSDPlus instance monitors the trunking channel, and this tunes the second FMP+DSD instance to the frequency currently active in the trunking system.
Corrosive also explains how people who are subscribed to RadioReference can download pre-populated data files that will allow the DSDPlus event log to display talkgroup information so that you can see who is talking to who.
Digital Radio Scanning With DSDPlus Setup Fastlane | Tracking Phase 1 P25 Trunking System Tutorial
Thanks to Tony C who wrote in and wanted to share a method that he's found to listen to multiple DMR digital voice channels in Linux. DSD+ is a Windows program that can be used to decode DMR. Although for Windows it is possible to use in Linux via the emulator known as Wine, and pipe the digital audio to it from GQRX. In the quote below, DSD+ "FL" is short for "Fast Lane" which is DSD+'s paid beta service that you can join to get newer code with more features. Tony writes:
I believe that can bridge the gap between using Linux with the ease of use programs of windows. As I am sure we both can attest that setting up trunk tracking / anything SDR is not as easy on Linux as it is on windows. For example, DSDplus FL makes it extremely easy to identify/decode DMR networks. There are similar things that can be done on Linux, but as I stated, it isn’t as easy to setup.
So the method that I setup and have been using successfully, using Ubuntu and a HackRF, setting up DSDplus 2.98 on wine, that gets audio piped from GQRX using a virtual sink as outlined in https://www.hagensieker.com/wordpress/2018/04/29/dsd-in-ubuntu-18-04/. It was a great blog, but I felt that it was incomplete when trying to get all the voice traffic passed on a network, as it only works on 1 channel at a time.
So I found the control channel for the network and created 5 bookmarks in GQRX and gave them the tag “DMR”. From there I downloaded gqrx scanner https://github.com/neural75/gqrx-scanner followed the install and setup instructions. From there I activated the scanner and GQRX will cycle through the frequencies and when voice traffic is passed, it will stop, and DSDPLUS via wine will decode and record the audio.
[The screenshot] example was for P25, but it has worked in connect+ as well, the only thing is that you cannot bookmark the control channel. I know other options exist out there such as SDRtrunk / op25 which I have used, but I believe this provides a good alternative to those who have used windows and are comfortable with the ease of use of dsdplus FL but want to be on the Linux OS.
During the Cyberspectrum Wireless Village talks a few days ago Gavin Rozzi gave a talk about his online RTLSDR-based trunking scanner website at ocradio.live. Recently he wrote in and wanted to share a little more about his system. He writes:
[The talk focuses] on my experience implementing several open source software packages to create an online RTLSDR-based trunking scanner website, https://ocradio.live/ that serves the part of New Jersey that I live in. Using multiple RTLSDR receiving locations, the site is demodulating, recording, and timeshifting multiple talkgroups of local and state trunked radio systems to create a live streaming service and archive of past scanner calls. Data from the site is also accessible over a REST API and we allow the creation of custom scan lists. My presentation is going to center on the advantages the site has over traditional hardware scanners and some of the technical challenges that we had to overcome to get the project off the ground.
Most police departments is the USA have now upgraded or are in the process of upgrading their radio systems to P25 Phase 2 digital radio. The frequencies can easily be received with an RTL-SDR, but a decoder is required to be able to actually listen to the voice. Software like SDRTrunk and DSDPlus can decode P25 Phase 1, but at the moment the only software that is capable of decoding P25 Phase 1 AND 2 is a program called OP25. However, OP25 has a reputation of being fairly difficult to set up as it does not have a simple to use GUI, and requires Linux.
Over on John's Tech Blog, John has uploaded a very helpful step by step tutorial that should help with those trying to get OP25 to work. The tutorial assumes that you have Ubuntu 18.04 already installed, and then starts from downloading and installing OP25. The next steps involve setting up OP25 for the particular system in your area, which mostly involves just editing a spreadsheet to input frequency data from radioreference.com. John also mentions that he's been able to get OP25 running perfectly on a Raspberry Pi 3 B+ as well, with less than 40% CPU usage.
In the video below John reviews some of the steps, and shows OP25 running and decoding voice.
Over on his blog John Hagensieker has uploaded a tutorial that shows how to set up SDRTrunk with RTL-SDR dongles. SDRTrunk is an application that allows you to follow trunked radio conversations, and decode some digital voice protocols such as P25 Phase 1. It is similar to Unitrunker and DSDPlus combined into one program. It is also Java based so it is cross platform and so can be used on Linux and MacOS systems as well.
John’s tutorial contains many useful screenshots, so it should be great for a beginner. He starts from the beginning, with finding trunking frequencies over on radioreference.com, then goes on to the installation and use on Linux. He also later explains how the Airspy can be used instead of multiple RTL-SDR to cover 10 MHz of bandwidth so that multiple systems can be monitored.