The FCC has now made FM CB radio legal in the USA. Is the new FM CB mode a game changer for this old school staple of two-way radio communication? The answer depends on who you talk to – those selling new radios to truckers will most likely say yes. As overland and off-road users of two-way radio, we’re not so sure the new FM CB radios are really all they’re cracked up to be. This article will hopefully shed some light on the pros and cons of FM CB and how it compares to GMRS (General Mobile Radio Service) radio – which already uses FM modulation.
President Thomas FCC CB with FM and AM mode.
Good Ole CB Radio Gets an Upgrade
CB radios haven’t really changed much since the 1970s, aside from getting 40 vs. 23 channels. For Jeepers and others who travel off-road, CB radio has long been the go-to radio for communication among groups of vehicles, especially in areas where there’s no cell phone coverage. Often plagued by “skip” interference, foul language and lack of consistent range, CB is quickly being replaced with GMRS radios in the Jeep and off-road community. A couple years ago, Jeep Jamboree USA announced that all off-road communications at the event would be on FRS/GMRS instead of CB. Was this premature, with the new FM CB mode coming out? Let’s look at some pros and cons of the new FM CB radios vs. GMRS.
How The New FM CB Mode Differs From Old AM CB’s
FM stands for “frequency modulation”. Technically speaking, FM is a way of encoding information (your voice) in a carrier wave by varying its instantaneous frequency. With AM, used by old school CB, the amplitude of the wave is varied in proportion to that of the message signal. Having your voice sent over the airwaves by AM means that to decode, or hear it, the listener must sort through any other information competing with your voice in the transmission, (think lightning, power line noise, skip interference, etc).
The FM CB Mode Offers Reduced Noise – But Less Range
According to a report from the Department of Electrical Engineering and Computer Sciences at U.C. Berkeley – “Using FM modulation in the Citizens Band will provide an improved signal-to-noise ratio (about 25dB) with regards to man-made interference over AM.” FM modulation operates on the “capture effect”, in that the strongest, often closest signal is the one that’s heard. While you might understand the words of distant AM CB radio conversation mixed with others – not so with FM. You’ll only hear the strongest signal while on FM mode. Inability to make out distant competing signals can mean less usable communications range for FM CB radios vs. AM ones.
FM CB vs. GMRS – Which is Better?
For off-road use, most two way radio users simply just want to have reliable, noise free communications between Jeeps, etc., which makes the new FM CB radios a better choice than older ones using noisy AM. But, even though FM modulation is a more noise free mode for short range, an FM CB radio is still just a CB. The Citizens Band uses 11 meters, a band prone to worldwide “skip” interference every few years, and CB’s need longer, more obtrusive antennas to perform well.
Skip – FM signals will still “skip” and your local conversation can be overridden by someone as far as 1,000+ miles away at times. Some brands of illegal CB radio amplifiers or “linears” could theoretically work with the new FM CB’s, so the chances of interference from illegal stations when using this new mode may be pretty high, especially during a phenomenon known as the “solar cycle”, when the earth’s upper atmosphere gets all charged up – becoming sort of like a giant sheet of tinfoil – reflecting CB radio signals as far as worldwide. “Skip” does not occur on GMRS, which uses the UHF, or Ultra High Frequency part of the radio spectrum, compared to CB, which uses HF or High Frequency.
Potential For Radio Chaos – Users of older AM CB radios users won’t be able to understand someone who’s talking on the same channel while in FM mode, and vice versa. As more FM CB radios are sold, some informal agreement may come about as to which channels are for FM and which are for AM. Knowing CB radio like we do, we have little hope for this process being orderly.
GMRS Offers More Power For Off-Road Use
Off-road users with GMRS radios in their vehicles will still have several advantages over those using the new FM CB radios. The FCC only allows FM Citizens Band radios to use 4 watts of output power, compared to 50 watts for the General Mobile Radio Service. GMRS antennas are also typically much shorter than CB antennas, meaning you can have a less obtrusive (and more power efficient) antenna on your overland vehicle.
FM CB Radio Does Have Some Small Advantages Compared to GMRS…
For those die hard CB users out there who will “never leave CB”, having one of the new models that’s FM capable can give you a new mode to go to when local communications are overpowered by distant skip interference. Also, they can still talk to older CB radios, like those many long haul truckers use. Also, CB radios offer 40 channels – compared to GMRS radios, which only offer 22 channels.
No License – For many off-road users, the fact that CB radio doesn’t require a license as GMRS does is an advantage. CB is much less monitored by the FCC than GMRS, for better or for worse.
Longer frequency CB radio waves can sometimes travel longer distances than GMRS signals, especially in wide open country, although the higher power of GMRS may negate this advantage. We’ve used both FM and AM CB and GMRS, side by side, and in our experience, a well tuned 50 watt GMRS, connected to a high gain 5/8 wave antenna, will normally talk farther than a 4 watt CB. The only instance where CB works farther than a 50 watt GMRS is when using SSB mode, which isn’t available on many radios and not offered on any handhelds.
Reasons That GMRS is Better For Off-Road Than FM CB
- Most fixed-mount GMRS radios come with the ability to use “privacy tones” for use in crowded areas such as Moab, UT. These tones mute the squelch so only your own group’s calls are heard. CB radio’s don’t generally come with available privacy tones or “tone squelch”.
- Some GMRS radios are “repeater capable” allowing the user to use long range repeaters, which rebroadcast your signal over a wider areas. FM CB doesn’t offer this capability.
- GMRS antennas are shorter than CB antennas, and can offer a higher dB gain factor for the same size antenna – meaning more ERP (Effective Radiated Power).
- GMRS radios are compatible with widely available FRS and GMRS handhelds, sold in discount and outdoor stores.
- You’re less likely to hear foul language, or “skip” interference on GMRS channels vs. CB.
The Main Reason We Like GMRS vs. FM CB Radios For Overlanding
Besides more range, less foul language, etc., we like using GMRS radios to keep in touch when camping and off-roading for one main reason. Widely available handheld FRS and GMRS radios can be carried by everyone in our group, and can call our full power watt units in our vehicles. There are FM CB walkie-talkies for sale, such as the President Randy FCC handheld , which sells for around $140, but that’s not such a great deal when compared to a Baofeng UV-9G GMRS handheld which costs only about $40, and has better range and battery life than a handheld CB radio.
When We Use GMRS – When we get to our camp, one of us can grab a handheld, go off hiking, and easily call back to base camp from up to 5 miles or so, depending on terrain. Also, if we meet other overlanders who want to join up, chances are, they already have a FRS or GMRS radio onboard instead of a CB.
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The Bottom Line: GMRS and license free FRS radios are still better than FM CB Radio for most outdoor adventures. If you’re a long haul truck driver who already uses CB the new FM CB mode will come in handy when noise is a problem. Otherwise GMRS is still the way to go for a fixed-mount radio setup for recreational use. We don’t really see a market for FM CB radios in the overland community, especially when GMRS offers so many advantages.
Please remember that if you choose to go the GMRS route, a $35 fee is required for a 10 year family license.
For our full article on why we like GMRS vs. CB Radio see GMRS Advantages Over CB.
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