At DEF CON 26’s Cyberspectrum meetup, I presented on an entrepreneurial civic technology platform that revolutionized how residents access public safety information by leveraging software-defined radio technology to create a sophisticated web-based scanner system.

Presentation Overview

This talk explored the technical implementation and civic impact of a next-generation police scanner platform that transformed traditional radio monitoring into a modern, accessible digital service. The project demonstrated how open-source tools and software-defined radio (SDR) technology could create information infrastructure that outperformed commercial hardware scanners.

The Challenge: Fragmented Public Safety Information

Traditional approaches to monitoring public safety communications faced significant limitations:

Hardware Constraints: Commercial scanners were expensive, complex to program, and limited to monitoring one talkgroup at a time
Trunked Radio Complexity: Modern P25 trunked systems required specialized equipment and technical knowledge
Geographic Limitations: Multiple radio systems across a region meant coverage gaps
No Historical Access: Real-time only monitoring with no ability to review past transmissions
Accessibility Barriers: High cost and technical expertise excluded most residents from accessing public safety information

Technical Solution: Software-Defined Radio Platform

The project implemented a comprehensive SDR-based solution using the RTLSDR platform and open-source software:

Core Architecture

Radio Reception and Decoding

RTL-SDR dongles for signal reception across multiple frequencies
GNU Radio for signal processing and trunked system following
P25 decoder integration for digital voice extraction
Automated frequency tracking across trunked control channels

Multi-System Aggregation

Simultaneous monitoring of multiple radio systems
Intelligent talkgroup prioritization and recording
System-wide channel coverage exceeding hardware scanner capabilities
Real-time switching between active transmissions

Web-Based Interface

Browser-accessible player eliminating need for specialized hardware
Responsive design for desktop and mobile access
Intuitive navigation across agencies and talkgroups
Real-time status indicators for active channels

Time-Shifting Innovation

A key differentiator was implementing time-shifting capabilities:

Recording and Archival

Automated capture of all transmissions across monitored systems
Searchable historical archive of public safety communications
On-demand playback of past events and incidents
Retention policies respecting privacy while preserving public interest

Playback Features

Skip through quiet periods automatically
Jump between agencies and units
Review multiple perspectives on major incidents
Export functionality for research and accountability

Software-Defined Radio Advantages

The SDR approach provided numerous benefits over traditional hardware:

Cost Efficiency

Consumer-grade RTLSDR dongles at fraction of commercial scanner cost
Scalable to cover entire regions with minimal hardware investment
Software updates added features without new hardware purchases
Cloud hosting eliminated need for local infrastructure

Superior Performance

Parallel monitoring of multiple talkgroups simultaneously
Better audio quality through digital signal processing
More reliable signal acquisition in challenging RF environments
Automated system following without manual programming

Flexibility and Extensibility

Open-source software stack enabling rapid iteration
Custom algorithms for intelligent recording decisions
API-driven architecture for third-party integrations
Platform-agnostic implementation running on standard Linux servers

Civic Technology Impact

The platform represented a new type of local information source:

Public Safety Transparency

Real-time access to police, fire, and EMS communications
Historical records for accountability and oversight
Community awareness during emergencies and major incidents
Research tool for journalists and civic organizations

Information Democratization

Free public access to information previously requiring expensive equipment
Mobile-friendly interface accessible from any device
No technical knowledge required for residents to monitor their community
Equal access regardless of economic resources

New Information Paradigm

Shift from hobbyist scanning to civic infrastructure
Integration point for broader emergency information systems
Foundation for automated incident detection and alerting
Platform for community-engaged public safety

Technical Deep Dive Topics

The presentation covered detailed implementation topics:

RTL-SDR Configuration

Hardware selection and setup procedures
Antenna design and placement optimization
Multiple-receiver coordination
RF interference mitigation strategies

Trunking System Decoding

P25 Phase I and Phase II protocol handling
Control channel monitoring and decode
Dynamic frequency allocation tracking
Talkgroup identification and prioritization

Audio Processing Pipeline

Digital voice codec implementation
Audio enhancement and noise reduction
Compression for efficient storage and streaming
Real-time encoding for web delivery

Infrastructure Scaling

Multi-receiver coordination architecture
Distributed processing for geographic coverage
Database design for transmission metadata
CDN integration for reliable streaming

Performance Comparison: SDR vs Hardware Scanners

The platform demonstrated clear advantages:

Coverage

Monitor 10+ talkgroups simultaneously vs. 1-2 for hardware scanners
Track multiple systems across region vs. single-system limitation
Capture 95%+ of transmissions vs. frequent missed communications

Usability

Web interface vs. complex button combinations
Instant system updates vs. manual reprogramming
Searchable history vs. ephemeral monitoring
Multi-user access vs. single-device limitation

Cost

Sub-$100 per receiver vs. $400-800 for comparable hardware scanner
Free software vs. expensive proprietary systems
Cloud hosting vs. dedicated infrastructure investment

Open Source Components

The project built upon mature open-source tools:

RTL-SDR: Software-defined radio drivers and libraries
GNU Radio: Signal processing framework
OP25: P25 digital radio protocol decoder
FFmpeg: Audio encoding and streaming
PostgreSQL: Transmission metadata storage
nginx: Web server and streaming infrastructure

This open-source foundation enabled rapid development while ensuring the platform remained accessible and auditable.

Lessons Learned

Key insights from implementation and operation:

Technical Challenges

RF environment variability requiring dynamic adaptation
Balancing coverage breadth with recording quality
Managing storage costs for continuous archival
Ensuring reliable uptime for community-critical service

Policy Considerations

Privacy implications of archiving public communications
Legal frameworks for scanner operation and redistribution
Community engagement around transparency versus operational security
Sustainability models for ongoing operation

Unexpected Applications

Emergency management situational awareness
Academic research on public safety operations
Journalism investigations and reporting
Community organizing during disasters

Audience and Reception

Presented to DEF CON’s Cyberspectrum community—engineers, security researchers, and radio enthusiasts interested in:

Software-defined radio applications
Civic technology and transparency
Open-source infrastructure projects
Radio communications and protocol reverse engineering

The technical community appreciated both the engineering innovation and the civic application, with extensive Q&A on implementation details and scaling challenges.

Watch the Presentation

Watch on YouTube

About DEF CON and Cyberspectrum

DEF CON is one of the world’s largest and most notable hacker conventions, held annually in Las Vegas. DEF CON 26 took place August 9-12, 2018, bringing together security researchers, hackers, technologists, and enthusiasts from around the globe.

Cyberspectrum is a regular meetup at DEF CON focused on radio frequency (RF) hacking, software-defined radio, and wireless security research. The meetup provides a forum for presentations on cutting-edge radio technology applications and security implications.

Legacy and Impact

This project exemplified several themes that continue in my current work:

Building Public Infrastructure

The platform demonstrated how modern technology could create new types of civic infrastructure that improve transparency and community engagement—a principle that guides my work building government systems today.

Open Source Innovation

Leveraging open-source tools to solve public problems created solutions more accessible and sustainable than proprietary alternatives—an approach I continue to champion in government technology projects.

Technical Depth in Service of Civic Goals

The project showed that sophisticated technical implementation could directly serve community needs, bridging the gap between engineering excellence and public impact.

Entrepreneurial Problem-Solving

Identifying a gap in information access and building a novel technical solution represented the entrepreneurial approach to civic technology that characterizes my career path from independent projects to government leadership.

This project connects to broader work in civic technology and transparency:

OPRAmachine - Building platforms for government transparency
Open data initiatives - Making government information accessible
Community information systems - Creating infrastructure for local awareness
Technology innovation in public service - Applying modern tools to civic challenges

This presentation represented an early example of using innovative technology to reimagine how communities access and engage with public information—principles that continue to guide work in civic technology and digital government transformation.