Back in April 2019 we posted about Matt Mills' Radiocapture.com website which is a web service that you can feed that automatically captures analogue and digital trunked radio conversations with an RTL-SDR, and allows public users to play back conversations via the web interface. The Radiocapture page which shows what the software is capable of is also active at radiocapture.com/radio. 

Back in April Matt was fundraising via Patreon and hoping to make development of Radiocapture his day job, but unfortunately he's had to call it quits for now. Since he no longer has time to work on it, Matt has open sourced the RF side of the software. The software description reads:

[Radiocapture-rf] is capable of using multiple networked computers and multiple SDR radios to demodulate the control channel of P25, EDACS, and Motorola trunking systems, as well as some limited support (alpha quality) for scanning for systems, LTR trunking, and "police scanner" style audio capture.

It is designed to effectively scale to an infinite capacity of trunked systems, captured transmission volume, and dongle bandwidth (more dongles = more available bandwidth, more cpus = more channels and more systems). (There is one remaining feature to be implemented to really make this work well, dongle redis autodiscovery (frontend_connect should autodiscover and use available dongles) and splitting the rc_frontend/receiver.py into one process per dongle.

The frontend initializes the SDRs in whatever configured frequency range, and presents a server interface where clients can connect and request a specific channel be created and forward to them. The frontend will then attach a channel, and output to a UDP sink (might be something better now, I forget). On the backend side, a control_demodulator is listening to that sink and doing the actual RF demodulation, which is passed into redis for distribution to other services. The backend is effectively a bunch of microservices that work together to track & record all ongoing transmissions and do some amount of deduplication. This entire setup is designed such that it can be scaled across as many servers/computers as necessary (although there are a few caveats/things I never got around to implementing in how it actually works). Recorded transmissions are decorated with a metadata scheme in their mp3 tags that is designed to be able to be loaded into the Radiocapture.com database. Finally completed mp3s are dropped into an activemq queue for publishing.

Matt notes that the software in it's current state isn't considered as "ready to distribute" as you may need some decent experience with Linux and Python to get it up and running.

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.