Frequency modulation, or FM, is a different method for encoding information in a radio wave. It offer much clearer audio. With the changes that the FCC enacted in 2021, CB radios can now have FM as a possible mode. AM is still the default mode for all CBs.
Until very recently, all citizens band radios broadcast only on AM frequencies. Now, all that is changing. In September 2021, the Federal Communications Commission (FCC) approved the use of FM mode alongside AM mode and single-sideband (SSB) modes on citizens band (CB) radios. Truckers and amateur radio enthusiasts are touting this change as the biggest one to hit the industry in at least four decades.
What Is a CB Radio?
The fundamental nature of a CB radio allows a radio operator to transmit signals in two directions instead of simply receiving them, as is the case with regular radio service. CB radios are very popular among truck drivers and motor carriers, with millions of users taking advantage of this technology to communicate between vehicles.
How to Use an FM CB Radio
Until 2021, the only types of CB equipment manufactured for trucker and consumer use in the United States were AM-only and SSB radios. Adding FM mode to these types of older equipment won't be possible, but there are plenty of manufacturers already creating new two-way radios capable of receiving FM signals.
Differences Between AM, FM, and SSB Mode
The primary difference between SSB AM and FM radio is a matter of power output, or spectral
density. Modes change the way in which your voice is encoded in the radio wave. Each mode has pros and cons. SSB is the best for range, but the hardest to use. AM is the best for range at a slight cost of audio clarity. FM offers the best audio clarity, but will often have the worst range of the 3 modes. Think of your AM/FM stereo in your car. AM stations are typically used for talk-radio because clarity isn't as important as range. FM is where the music is because it sounds the best.
It's the same situation with AM and FM modes for CB.
FM radio is different from both double-sideband AM and SSB. It has a larger spectrum than the usual AM radio, which means the power output is spread out over a wider bandwidth. As a result, FM CB radios don't suffer from the same sound quality issues as traditional AM amateur radios, even with the same watts output. Most truck drivers find that they have a better user experience with the new FM radios since they create only minimal static and make it easier to hear.
Now Is the Time to Invest in New Radio Equipment
As the FCC approves FM for CB, now is the time for truckers and amateur radio enthusiasts to
start upgrading equipment. The change to citizens band radio service means that anyone with a
handheld radio manufactured before September 2021 will be unable to transmit and receive FM
Note here that it will, however, still be possible to transmit on AM bands or SSB bands with the right equipment. There are plenty of manufacturers with AM-only radios left in stock, so those who don't want to substantially change how they use CB radios can also purchase leftover goods at discount prices in 2022.
It's also worth noting that AM is still going to be the default mode for all CB's. FM and SSB are optional and will only be found on select models.
The Importance of Radio Location
As with everything in life, the switch to FM CB radios is not without its drawbacks. FM twoway
radios are fantastic at transmitting high-quality audio over short distances. They're great for line-
of-sight communications because the received power is sufficient and it's possible to sacrifice
some bandwidth to get better quality audio.
When the transmission needs to cover a greater distance, sacrificing bandwidth can become a problem. The bandwidth is constrained, which means it won't always be possible to maintain consistent radio service between two trucks with changing periodic locations. In this case, SSB may be a better operating mode for personal radio services.
Volume Adjustment and Channels
How FM Got Added to Citizens Band Radio
There have been plenty of examples of FM bandwidth use in CB radio history, just not in the
United States or North America, more generally. Cobra has been fighting for the addition of FM
to CB radios for years, but it was only in August when the company was joined by President
Electronics that the FCC reconsidered its stance. It issued a memorandum opinion along with
an order of reconsideration last August and officially reversed its FM ban in September.
The eventual decision made by the FCC was influenced by its recognition that adding FM capabilities to AM CB radios won't substantially change how they operate and will improve user experience. Amateur radio operators and truckers will still be able to use older equipment to transmit via AM and SSB, and will only need to purchase FM-capable mobile radios if they are interested in sending and receiving signals via this expanded bandwidth.
Frequently Asked Questions
Still wondering how the FCC's decision to allow FM transmissions on CB radios will impact everyday use? Here are a few answers to others' most frequently asked questions that could offer some clarity:
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A CB radio is usually AM. However, the FCC also recently approved the use of FM transmissions, which should be coming soon.
You can use FM on a CB radio only if it is equipped to send and receive FM transmissions. CB radios manufactured before September 2021 when the FCC approved FM transmission use are not FM-enabled.
The difference between AM and FM on CB radio is that AM tends to pick up interference and background noise, while FM focuses only on the strongest signal. As a result, you will only hear one voice in the cab at a time on the FM band, but it will be clearer.