Frequently Asked Questions – FM for CB Radio

The use of FM CB frequencies was approved in the U.S. in 2021. Learn about the differences, advantages, and equipment needed for FM CB radio:

Frequently Asked Questions

Can I use FM mode on CB radio?

Yes, you can now use FM mode on CB radios in the U.S.

Why are people excited about FM capabilities for CB radios?

Historically, one major limitation of CB radios has been the number of channels (or frequencies). Traditional CB radios only operate on 40 channels and in the following modes:

FM (Frequency Modulation) mode offers much better sound quality when communicating via radio and improves the CB experience by leaps and bounds. This is the biggest change to CB radio technology since its expansion from 23 to 40 channels in 1977.

FM mode is the best of all worlds when it comes to CB radio. The equipment is affordable, compatible with existing CB setups, and offers the best available sound quality due to the "capture effect," meaning that one strong signal is selected, and other signals are suppressed.

How did FM mode finally get approved for CB radio in the U.S.?

While FM mode is new to CB users in the U.S., it isn’t new to radio. AM/FM capable CB radios have been legal in Europe and several countries in other parts of the world for years, where FM is now the main mode of communication due to its superior sound quality.

Adding FM mode to CB radio in the U.S. was approved by the FCC thanks to the efforts of Cobra Electronics and our customers. We petitioned the Federal Communications Commission for a rule change to FCC Part 95 in 2016 and asked our customer base for feedback on their interest in using FM mode. We gathered input from many sources – including online CB radio forums, off-road vehicle clubs, distributors, and more – and the result was a resounding yes! With wide acceptance for allowing FM frequencies on CB radios by our customers, the FCC finally approved the change in September of 2021.

What’s the difference between AM and FM mode? Is it just like my car stereo?

Not exactly. In a car stereo, the AM stations occupy a completely different band (a specific range of frequencies in the radio frequency spectrum) than the FM stations. For a car stereo system, the FM band is located at a much higher frequency than the AM band, which contributes to improved sound quality. Radio frequencies are organized as follows:

  • FM frequencies range from 88.00 – 108.0MHz. This band is divided into 100 channels each, with individual stations accessed in 200kHz (or 0.2 MHz) steps. FM stations all end in .1, .3, .5, .7, or .9 (ex. FM 93.9, FM 98.7, FM 103.1).
  • AM frequencies range from 540 – 1700kHz, and individual stations can be accessed in 10kHz steps (ex. AM 670, AM 720, AM 1000).

FM mode sounds better on a car stereo because Frequency Modulation is more resistant to background noise pollution from other transmitters and atmospheric conditions like noisy power inputs, nearby power transformers, solar radiation, storms, etc.

On a CB radio, AM/FM operates a little differently. A CB radio’s frequency range is 26.965 – 27.405MHz and is broken up into 40 channels, with 10kHz steps. AM and FM signals can both occupy this same frequency band, traditionally used for AM and Single Side Band (SSB) modes.

Should my CB be on AM or FM mode?

The mode you should select for CB communication depends on your needs and the distance between users. The main advantage of AM for CB is longer range, and the main advantage of FM is sound quality at close range. Having a dual mode AM/FM CB radio allows the user to modulate between the two types of channels to find and use the best signal for communication based on their needs.

For example, if the sound is coming through muffled while communicating locally on an AM channel, switching to FM mode on the same frequency can strengthen the signal and greatly improve the volume and clarity of the sound. But if you’re trying to communicate with other CB users at greater distances, AM frequencies will likely be more reliable.

Will I need a new antenna?

No, your existing antennae systems will work for FM mode.

What frequency is used for CB FM mode?

FM mode operates withing the same 40-channel frequency band traditionally used for AM on CB radio: 26.965 – 27.405MHz.

Does FM require special hardware or a different radio design? Will an AM/FM CB radio work with my existing or older CB setups?

Yes, the way FM signals are received and processed is different from AM mode and requires specific FM compatible equipment. This equipment can be retrofitted to work with existing CB setups, so you will not need to purchase all new equipment to add FM mode to your CB .

Can I still talk to people on my current AM CB?

Yes, you will still be able to communicate using AM mode as normal. Because AM and FM modes will share frequencies, users will be able to share channels across modes and will likely be able to hear incoming signals from the mode not currently in use. AM-only users will be limited to AM channels, so if FM users are occupying a specific channel, AM users may not be able to join in the conversation.

What is SSB and how does it relate to AM and FM?

CB radio allows for the use of several different types of modulation methods or "modes." Single Side Band or SSB modulation is a type of amplitude modulation that uses less than half the bandwidth of a traditional AM signal. SBB is divided into Upper Side Band and Lower Side Band. SSB allows for communication over longer distances, including international.

While SSB uses less bandwidth, FM mode occupies the widest frequency band and offers much richer sound quality. SBB has a longer effective range than FM, but as an AM mode, it is still subject to background noise and interference.

Keep in mind that SSB radios require additional hardware and are a more expensive option for CB radio, typically costing $30 – $50 and up more than AM-only radio units.

SSB is also more complex to operate and is typically only recommended for advanced users; it includes a "clarifier" control that requires the user to manually tune in to an incoming signal each time.

Why would I want FM for my CB radio?

FM mode offers better audio quality for CB users and is easy to use. It offers clear, noise-free, and more intelligible two-way communications versus AM, which is why FM is popular with CB users in other countries and in other radio bands. FM mode also greatly reduces background noise and interference.

You may also want to use FM mode to communicate with other users, as traditional AM-only units will not be able join the conversation on FM frequencies.

Should I upgrade my CB now?

Now is a great time to upgrade your CB setup with AM/FM compatibility to connect with other FM users in the U.S. Having FM mode available can enhance the CB radio experience with superior sound quality. Plus, you can find new communities of CB users on FM channels!

If you’re ready to upgrade your CB experience, explore Cobra Pro AM/FM compatible CB radios today.