Skip to content
This site is not affiliated with or endorsed by TriMet
rosecitytransit.org: transit in the rose city...maybe even Rose City Transit

About the TriMet scanner

It uses 2 RTL-SDRs, low-cost USB Realtek software-defined radios originally meant for European digital broadcast TV reception. 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. Trunk Recorder is able to take that raw signal and decode multiple channels from it at the same time.

Due to technical difficulties, only the Council Crest radio tower of TriMet's radio system is being monitored. This means that calls to buses which are connected to one of the other 5 radio towers do not get recorded. Some bus calls on the Mt. Scott site are being recorded on a different computer (using DSDPlus) and are transferred after midnight. As of 3/12/2021, Portland Streetcar calls on the City of Portland's radio system are also being recorded using DSDPlus and are transferred after every hour.

I have a list of radios seen and bus radio events (calls, affiliations, etc) are being logged and are viewable on a map (using the same vehicle location data that my SystemMapper app uses).

The HTML is based on:
HTML5 Audio and Video and how to make a playlist
HTML5 Audio Playlist
HTML audio tag
Live version:
Google Maps util.js
Javascript - Append HTML to container element without innerHTML

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

decoding rate chart

2017 recordings per day 2018 recordings per day 2019 recordings per day 2019 recordings currently present 2020 recordings per day


By Jason McHuff, rctmail@jasonmchuff.net