CB Radios: AM or FM?

CB (Citizens Band) radios traditionally use AM (Amplitude Modulation) or SSB (Single Side Band) modulation schemes for communication.

However, FM (Frequency Modulation) has been introduced and is permissible for use in some regions, including parts of Europe.

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CB Radio Modulation Types

  • AM: The most common modulation type used by CB radios, especially in the United States, where CB radio originated. It modulates the amplitude of the carrier signal in accordance with the input signal.
  • SSB: This is a form of AM that allows for more efficient use of power and bandwidth. There are two types of SSB: Upper Side Band (USB) and Lower Side Band (LSB). SSB is favored for its range and clarity, especially over long distances.
  • FM: Less common in CB radios, FM is mostly used where it’s specifically allowed by local regulations. FM modulates the frequency of the carrier signal rather than the amplitude and is generally considered to provide clearer sound quality with less susceptibility to noise compared to AM.

Regional Differences

  • United States: The FCC (Federal Communications Commission) regulates CB radio usage, which traditionally has not included FM for the standard 40 CB channels.
  • Europe: Some European countries allow the use of FM on CB radios. For example, the UK permits FM on CB radios, providing an alternative to the traditionally used AM and SSB.

Advantages of FM in CB Radios

  • Sound Quality: FM typically offers better sound quality and less static than AM, making communications clearer, especially in noisy environments.
  • Interference Resistance: FM is more resistant to electrical noise and interference.

Conclusion

While FM is not traditionally associated with CB radios, especially in the U.S., it is used in some regions and offers advantages in terms of audio clarity and interference resistance.

If you are considering purchasing a CB radio or using one in different parts of the world, it’s important to check the local regulations regarding allowable modulation types and frequencies to ensure compliance and optimal operation.

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