DIY Police Scanner With SDRs and Open Source Software

The talk looks at how US police radio traffic can be monitored independently with a home-built system instead of relying on paid scanners or limited subscription streams. Most agencies use the digital, trunked Project 25 standard, where conversations move between frequencies across talk groups, so a listener has to follow calls as they are reassigned. The speaker explains why commercial options fall short for someone who wants every unencrypted talk group, and why archiving matters.

The described setup uses a home machine with several RTL-SDR dongles running Trunk Recorder to decode and save calls, which then upload to a separate web app, RDIO-Scanner, for live listening and searching recent audio. The manual preparation covers finding the local system and control channel on RadioReference, measuring each dongle's frequency error, and building the talk group list. An Ansible workflow then automates installing and configuring the components. Hardware notes cover a four-dongle, four-core build, CPU and storage use, the effect of sample rate on load, and how a cron job manages archive retention.

The closing section focuses on practical use. Listeners should expect disturbing material, learn the lingo, and remember that radio claims can be false, so information should be corroborated before it is shared. The speaker places the feed within an intelligence cycle and urges advocacy for keeping non-sensitive talk groups unencrypted. The presenter said the playbooks and supporting scripts would be released afterward.