Software Defined Radio with HackRF, Lesson One

Introduction

• Presenter: Michael Ossmann from Great Scott Gadgets
• Topic: Introduction to Software Defined Radio (SDR) using HackRF
• Purpose: Course aimed at teaching SDR through a series of videos focusing on digital signal processing and radio functions

Overview of Software Defined Radio (SDR)

• Definition: Use of digital signal processing to implement radio functions
• Capabilities: Create transmitters or receivers for any radio signal using software with hardware like HackRF and a computer

HackRF One

• Description: A Software Defined Radio peripheral that connects via USB
• Functions: Transmit and receive signals over a wide range of frequencies
• Comparison: Similar to a sound card but for radio signals

Course Background

• Origin: Derived from a two-day class taught at information security conferences
• Approach: Focus on introducing SDR, probing the security of radio systems
• Audience: Geared towards those interested in SDR, not limited to security professionals
• Teaching Style: Informal, open content, available online

Course Structure

• Website: greatscottgadgets.com/sdr
  • Content: Videos, text, exercises, and corrections
• Tools Used:
  • GNU Radio Companion (GRC): A graphical user interface for GNU Radio
  • GNU Radio: Allows creation of software radio programs
• Focus: Fundamentals of digital signal processing, HackRF as primary hardware tool

Lesson One: Building an FM Radio Receiver

Exercise Overview

• Objective: Create an FM radio receiver using GNU Radio Companion
• Steps:
  1. Set Up: Use osmocom source block to enable the HackRF to receive mode and stream samples
  2. Visualization: Use WX GUI FFT sync to visualize frequency components
  3. Configurations: Adjust sample rate, frequency, and gain settings in GNU Radio
  4. Flow Graph Execution: Generate Python code and execute to visualize live radio data

Advanced Flow Graph Adjustments

• Filters: Add low pass filter, set cutoff frequency, transition width
• Resampling: Use rational resampler for sample rate adjustments
• Demodulation: Use wbfm receive block to convert radio signals to audio
• Audio Output: Use audio sync to output sound

User Interface Enhancements

• Volume Control: Add WX GUI slider for real-time audio gain adjustment
• Channel Tuning: Suggest adding a slider for real-time channel frequency adjustment

Performance Considerations

• Optimization: Adjust sampling rates based on hardware capabilities
• Troubleshooting: Address issues with CPU load and USB interface speed

Homework

• Tasks:
  • Try out Pentoo Linux
  • Replicate the flow graph
  • Add a GUI slider for channel frequency
  • Listen to two radio stations simultaneously
• Resources: Homework details and hints available on the course website

Conclusion

• Next Steps: Anticipate lesson two
• Note: Corrections and additional resources will be posted on the course website.

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• Key takeaway: This lesson provides a hands-on introduction to building an FM radio receiver, enhancing understanding of SDR and GRC.