Case Study 2: 60Hz Humming Noise on Certain Frequencies

Symptom:

  • A distinct hum at multiples of 60Hz (50Hz in some regions).

  • The noise is stronger on some bands than others.

Analysis:

  • This is likely power-line interference, possibly from poor grounding, power supplies, or nearby transmission lines.

  • Nearby appliances, dimmers, or solar inverters could also be culprits.

Mitigation Steps:

  1. Power Down Test:

  • Turn off all breakers in your home, leaving only the radio on battery power.

  • If the noise disappears, it’s inside your home. If not, it’s external.

  1. Use a Portable AM Radio:

  • Tune to a quiet frequency and walk around.

  • If the noise gets stronger near power lines, suspect arcing insulators.

  1. Mitigate Internally:

  • Add ferrites to power cords of computers, routers, and LED lights.

  • Replace noisy switching power supplies with linear ones.

  • Improve station grounding with a dedicated RF ground.

  1. Mitigate Externally:

  • If a power line is the cause, document the issue and report it to the power company.

  • Use a small loop antenna to confirm directional noise sources.