Ice Radio Products

Fighting Back Against Broadcast Band (BCB) Interference

Broadcast band interference (BCB) is a common issue for radio operators, often caused by powerful nearby AM broadcast stations transmitting in the 550 kHz to 1,700 kHz range. If you frequently hear music or commercials far outside the AM band, the source is likely a local station overpowering your receiver. In severe cases, the station can be heard every few kilohertz across the HF spectrum.

How to Identify and Combat BCB Interference:

  1. Identify the Type of Interference

    • Fundamental Overload: If the AM station’s signal floods your receiver across many frequencies, it’s likely RF voltage overload from the station’s primary transmission.
    • Harmonics: If you hear interference at intervals (e.g., 1,200 kHz, 2,400 kHz, etc.), the station is producing harmonic radiation—a weaker signal on multiples of its main frequency.

  2. Overload Interference Solution

    • Use a BCB filter to block the interfering station. Choose a filter that places the station deep within the stopband for maximum rejection (often providing 70 dB or more attenuation). This can significantly reduce or eliminate the interference.

  3. Harmonic Interference Solution

    • Contact the offending station’s chief engineer to report the issue. Stations are required to filter harmonics but may claim to meet FCC specifications.
    • Be polite and diplomatic—request a review of their transmitter’s output.
    • If the station complies with FCC rules, they are not obligated to assist further, but cooperative engagement may yield results.

  4. Rare Cases – Re-radiation and Power Line Interference

    • In rare instances, AM signals may mix with power lines or telephone wires.
    • Tracking down these sources often requires technical expertise or specialized equipment. A local radio club can offer assistance.

Additional Measures at Your Station:

  • Grounding and Shielding – Ensure your equipment is properly grounded and shielded.
  • Antenna Choice – Use horizontally polarized antennas to reduce vertically-polarized AM interference.
  • Bandpass Filters and Attenuators – Install HF bandpass filters or attenuators to minimize signal bleed from strong AM stations.

By combining filtering, grounding, and diplomacy, you can significantly reduce BCB interference and improve your radio reception experience.