The addition of FM to authorized CB transmitters created more options for a service once associated primarily with AM and SSB. But radio compatibility still matters.
FM is legal on compliant CB radios
The FCC amended its CB rules in 2021 to permit FM voice emission on certified equipment. That does not mean an arbitrary converted radio is permitted, nor does it change the shared nature of the 40 channels.
Does FM work with old CB radios?
An FM transmission cannot be correctly understood by a receiver operating in AM mode. Both stations need compatible mode settings. If the people you talk to use AM-only radios, AM remains the practical common denominator.
FM power limits
The U.S. maximum mean carrier power remains 4 watts for FM and AM CB transmissions. SSB has a different limit of 12 watts PEP. The rules also address emissions and certified equipment.
Should you buy AM/FM or AM/FM/SSB?
Choose based on whom you contact and whether you are interested in weak-signal DX. The antenna, installation quality and nearby activity are at least as important as extra radio modes.
Read our AM/FM/SSB comparison. Official rule: 47 CFR § 95.967.