HF Noise Identification and Mitigation Guide

Using a Software-Defined Radio with ka9q-radio and ka9q-web to identify and mitigate controllable noise interfering with HF signal reception.

Fundamentals

• Natural Noise Sources
  • Earth Noise
  • Atmospheric Noise
  • Ionospheric Noise & Effects
  • Galactic Noise
• Man-Made Noise (Electromagnetic Pollution)
  • QRM
  • Power Line Noise
  • Switching Power Supply Noise
  • Industrial & Consumer Electronics Interference
  • Solar Panel & Inverter Noise
• Receiver & Station-Generated Noise
  • Thermal Noise
  • Common Mode Current Noise
  • Intermodulation & Mixing Products
• Digital & Communication-Related Noise
  • Broadband Data Emissions (PLC, DSL, Ethernet)
  • Switching Digital Logic Noise
• Common HF Noise Sources
  • Power Line Noise
  • Switched-mode Power Supplies
  • LED Lighting
  • Solar Inverters
  • Computers and Peripherals
  • Cable TV Systems
  • Other Neighboring Devices
  • Timing Signals from GPSDOs
• Other Basic Noise Types
  • Common Mode Noise
  • Propagated Noise
  • Ground Loop Noise
• Important Definitions
  • Noise Floor
  • Antenna Factor
  • Noise Factor
  • Noise Figure
  • Dynamic Range
  • ITU Noise

Tools & Techniques

• Noise Detection and Measurement
  • Software-Defined Radios
  • Analog Receivers (AM, SSB, CW-capable radios)
  • Oscilloscope with FFT (Fast Fourier Transform) Capability
  • Stand-alone Spectrum Analyzers
  • Field Strength Meters
  • Current Probes & RF Clamp Meters
• Noise Source Identification Techniques
  • Direction-Finding Methods
  • Noise-Hunting with Portable Receivers
  • Controlled Power-Down Testing
  • Conducted vs. Radiated Noise Testing
• Noise Mitigation Techniques
  • Ferrite Chokes & Toroids
  • Common-Mode Chokes
  • Shielding & Filtering
  • Antenna Placement & Orientation

Strategies & Tactics

• General Identification & Mitigation Strategies
  • Identifying RF Noise
  • Mitigation Strategies
  • A layered approach:
• Case Study 1: Waterfall Changes When Moving a Feedline
  • Symptom:
  • Analysis:
  • Mitigation Steps:
• Case Study 2: 60Hz Humming Noise on Certain Frequencies
  • Symptom:
  • Analysis:
  • Mitigation Steps:
• Case Study 3: Periodic Short-Duration Pops in Audio
  • Symptom:
  • Analysis:
  • Mitigation Steps:
• Case Study 4: Repeating Spectral Humps at 1.8MHz Intervals
  • Symptom:
  • Analysis:
  • Mitigation Steps:
• Case Study 5: Noise Floor from DC to 60MHz is Higher than ITU Models Predict
  • Symptom:
  • Analysis:
  • Mitigation Steps:
• Case Study 6: Suspected FM Broadcast Station Interference
  • Symptom:
  • Step 1: Identify Artifacts from FM Broadcast Stations
  • Step 2: Investigate the SDR’s Sampling Rate and Front-End Behavior
  • Step 3: Verify the FM Source
  • Step 4: Mitigation Techniques
  • Conclusion
• Case Study 7: Noise Heaps
  • Symptom:
  • Analysis:
  • Mitigation Steps:

Resources

• External Links
• Miscellaneous Notes
  • From Glenn Elmore N6GN:
  • From Philip Barnard VK7JJ
• Contributors