About NWI Scanner
nwiscanner.com · Northwest Indiana Public Safety Scanner Archive
21
Total Runs
39101
Transmissions
20
Transcribed
21
Talkgroups
Last run active TGs
Jasper County Sheriff Dispatch
Jasper EMS
Jasper County Fire Dispatch
Valparaiso Dispatch
Porter County Fire Dispatch
Portage Dispatch
Porter Sheriff Dispatch
Portage/Valpo Fire - Talkaround
Porter Chesterton Police Dispatch
Portage Fire Fireground
Porter Countywide Fire/EMS Talkaround
Michigan City Police Dispatch
Michigan City Fire Dispatch
NWI Scanner is a publicly accessible archive of unencrypted public safety radio
communications received via software-defined radio (SDR) in Northwest Indiana.
The site captures transmissions from Porter, La Porte, Starke, Jasper, and Newton counties
on the Indiana STARCOM21 P25 Phase II trunked radio system, transcribes them using
AI-powered speech recognition, and makes them searchable.
This is an independent, community-operated project with no affiliation with any government
agency, public safety department, or commercial service.
1
A software-defined radio (SDR) dongle receives the RF signal, and SDRTrunk decodes the Indiana STARCOM21 P25 Phase II trunked system in real time. The system follows control channel traffic to track which talkgroups are active, automatically tuning to each voice channel as transmissions occur. Every individual transmission is saved as a WAV file tagged with talkgroup ID, timestamp, and unit ID where available. The receiver runs continuously, 24 hours a day.
2
Twice daily, a script collects all WAV clips recorded since the last run and merges them into a single master recording using SoX. During this process the audio is normalized to a consistent volume level, leading and trailing silence is trimmed from each clip, and a small gap is inserted between transmissions for readability. A JSON log is produced alongside the audio that maps every clip to its exact wall-clock timestamp and talkgroup — this is what powers the click-to-seek feature in the audio player.
3
The merged audio is passed through whisper.cpp, a fast local implementation of OpenAI's Whisper speech recognition model. Transcription runs entirely on-device — no audio is sent to any external service. Raw Whisper output is then post-processed through a custom 3645-entry correction dictionary built specifically for this system. The dictionary corrects common mishearings of 10-codes, agency names, unit identifiers, street names, and local place names across Northwest Indiana. Without it, Whisper frequently mishears radio-specific language.
4
Completed runs are synced from the local recording machine to the public web server. Transcripts are parsed, annotated with talkgroup metadata, and indexed in a SQLite full-text search database. The Flask web app serves the archive, audio player, and search interface. Clicking any line in a transcript seeks the audio player to that exact moment. All transcript text is fully searchable across the entire archive from the search bar at the top of the page.
Reception covers the Indiana STARCOM21 system serving Porter, La Porte, Starke, Jasper,
and Newton counties, along with regional talkgroups for Indiana State Police, Indiana Toll Road,
Indiana Dunes National Park, DNR, and air medical services.
Reception Area · NW Indiana
Porter County
10
Talkgroups
La Porte County
6
Talkgroups
Jasper County
3
Talkgroups
Newton County
1
Talkgroups
Regional / Statewide
1
Talkgroups
All transmissions monitored and published on this site are unencrypted public safety
communications broadcast on licensed radio frequencies. Reception of these signals is
lawful under federal law. Publication of unencrypted radio communications is permitted
under 47 U.S.C. § 605 and the Electronic Communications
Privacy Act, which explicitly excludes unencrypted radio communications from its prohibitions.
This site is operated solely for educational, research, and public interest purposes.
No private communications are intercepted or published. No encrypted transmissions
are decoded or published.
Transcripts are generated by machine learning software and may contain errors,
including misrecognized words, incorrect agency names, and inaccurate location information.
Always verify transcript content against the original audio before relying on it for any purpose.
Do not use scanner audio or transcripts as a substitute for calling 911.
If you witness an emergency, contact your local emergency services directly.
