About the King County Metro Transit radio scanner

It uses RTL-SDRs, low-cost USB Realtek software-defined radios originally meant for European digital broadcast TV reception, specifically 2 NooElec NESDR SMArt receivers. Unlike regular radios which can only capture one frequency at a time, these devices are able to see 2-3 MHz of spectrum and pass all of it to a computer program for processing.

The Trunk Recorder program is able to take that raw signal and decode multiple channels from it at the same time.

The King County Metro Transit Trunking System uses APCO P25 Phase II trunking (Wikipedia, RadioReference) and Trunk Recorder was one of the first programs to understand the protocol.

Columns are as follows:

This site was created by and is maintained from afar by Jason McHuff of rosecitytransit.org and @rosecitytransit. The HTML is based on:
HTML5 Audio and Video and how to make a playlist
HTML5 Audio Playlist
HTML audio tag
Google Maps util.js
Javascript - Append HTML to container element without innerHTML

Code available on GitHub at rosecitytransit/trunk-recorder:kcmscanner

None of this is in any way affiliated with or endorsed by King County.

Link Light Rail, etc channel

From 8/4/2019-2/24/2021, there was a channel for Link Light Rail, Transit Police and other groups that use the Seattle-King County Public Safety (KCERS) radio system. This audio comes from a PSR-400 radio scanner which is scanning all of the transit-related channels on the system and, unfortunately, it is not possible to save which one is currently active.

As of July 2020, those with a Radio Reference/Brodcastify account can also listen to these channels there:

(Police: Tactical, Sound Transit Security, Transit Tunnel Security 2, Transit Tunnel Security 1 are not publicly available on Broadcastify)

In addition, both the King County Metro Transit and Seattle-King County Public Safety (KCERS) systems are now available on OpenMHz.

2017 recordings per day2018 recordings per day 2019 recordings per day2019 recordings now present 2020 recordings per day
Link Light Rail, etc recordings per day2020 Link Light Rail, etc recordings per day

View of the radio spectrum in the area of the King County Metro Transit Trunking System as seen by rtl_power: