Citizens band radios can break the boredom of a lonely drive, alert you to problems on the road ahead, and allow you to reach emergency services quickly. Their convenience and usefulness has kept CB radios in truck cabs for decades. However, the performance of a CB radio is dependent on its range, which can vary tremendously according to various factors like your equipment and the terrain. To maximize the range of your CB radio, it helps to first understand its limits. Once you understand what your CB radio and antenna can do, you can set them up in a way that maximizes your transmission’s range and clarity.
In this article, we’ll examine the main factors impacting your CB’s performance and provide useful solutions to help you increase your range in an effective way.
What is the maximum range of a CB radio?
There’s no single, definitive answer to this question. Anyone can set up a CB radio and begin transmitting immediately; however, determining your maximum range is more complex. CB radios are a two-way street, so your transmission range is only half of the equation. Every person you talk to must be able to reach you, too. Taking drastic measures to extend your range pays diminishing returns because it’s likely that someone who hears you from far away will not have enough range to reply.
Back in the 1940s when CB radios were established, the FCC wanted to provide a radio system for civilian use with approximately seven miles of coverage. Your official CB radio range is a circle radiating out from your antenna for seven miles in all directions. Quality CB radios and antennas achieve this distance easily.
Certain conditions can make it possible for your 4-watt CB signal to reach radios hundreds of miles away. CB radio waves can bounce off the ionosphere and travel much farther. Night-time transmissions may exceed the seven-mile range because typically there are fewer radios transmitting at night. These long-range connections are unreliable, often lasting only a few minutes; but sometimes they do last longer, especially if both parties are parked or using base stations.
Of course, transmission range is hampered by mountains, forests, and densely packed buildings. CB signals will bounce off of obstructions like mountains, and trees can act like antennas, soaking up your signal. In wide open spaces, your transmissions might easily travel further than seven miles; in mountainous and especially forested areas, your range may be much shorter.
The Legal Limits Of CB Radio
The Federal Communications Commission used to require licensing for CB radios. However, because millions of users ignored the requirement, the FCC discontinued licensing back in the 1980s. Today, anyone can own and use a CB radio, but that doesn’t mean there are no restrictions.
The radio frequency (RF) spectrum is a lot like land – simply put, they’re not making any more of it. The RF spectrum is carefully regulated by the FCC so that each category of users has sufficient bandwidth for their needs. The RF spectrum map assigns specific bandwidths to various users like the military, first responders, civilians, and businesses. This ensures that critical services can communicate at all times without interference from things like cordless phones or amateur radio operators. The FCC has strict rules limiting CB operators to a low power output and a certain range of frequencies.
CB radio systems are allowed to transmit on 40 channels that range between 26 MHz and 27 MHz. Since CB radios are built to talk to each other, they are designed to use the specified 40 CB channels. However, the CB band is allocated differently in other countries, so foreign-made CB radios may not automatically reach other CB radios on US roads; this is important to keep in mind when shopping online.
There are several alternatives to citizen’s band radios that are able to access additional frequencies:
- Amateur radio (known as ham radio or 10-meter radio) has a frequency range of 28-29 MHz. This service requires a license and can transmit for thousands of miles.
- General Mobile Radio Service (GMRS) ranges from 462 to 467 MHz. It also requires a license and has some usage restrictions, but higher wattage gives it better range, and GMRS repeaters can be used to extend that even further.
- FRS or Family Radio Service provides two-way radio communications without a license. It relies on handheld radios in the GMRS band. They have a maximum power of two watts and a range of a couple of miles at best.
- Multi-Use Radio Service (MURS network) was created by the FCC in 2000. This UHF band was designed for home or business use with handheld radios and is also limited to 2 watts maximum power.
Disclaimer: Many of these alternative radio systems are limited to line of sight because their frequency band is higher than that of CB radios. They’re not designed for long-range communications.
The other important factor in CB range is power; the FCC limits CB radios to 4 watts of power. More than anything else, this low power requirement limits the longest range your radio can reach. Why is the power restricted on the CB radio band? There are a number of reasons.
- Short range communication: It provides a reasonable range for communications on highways, which was CB radio’s original purpose.
- Safety: 4 watts is low enough that amateurs with no training can attach and detach antennas without shocking themselves.
- Battery life: Low power use is not a big drain on vehicle batteries.
Some operators use an amplifier to boost the range of a CB radio. Adding an amplifier between the radio and antenna can boost your radio signal many times higher than the standard 4 watts. However, you will need a second battery to run the amplifier; check the specifications of your CB antenna to make sure it can handle the excess power.
It’s fairly easy to extend your range with extra equipment. But CB radios are two-way communication. You might amplify your radio to reach operators four counties away but without an amplifier on their end, they won’t be able to respond. And of course, being caught transmitting beyond the seven-mile range limit could result in a stiff FCC fine. It’s probably best to stick with legal gear, just like the people you plan to communicate with.
The Physical Limits Of CB Equipment
In addition to the legal limitations placed on CB radios, there are other limits to their maximum range caused by the laws of physics.
It’s no surprise that CB radios transmit farther on flat land than in mountains. While many radio waves travel in straight lines, CB wavelengths can reflect off things like buildings and mountains. As they ricochet around they lose power, so a radio wave that bounces off a bluff cannot travel as far as it would on an open plain. Transmissions are also unreliable in situations where the waves bounce off the landscape. If one or both parties are moving, the waves will shift and communication between the two radios can come and go erratically.
Height Above Average Terrain
Height above average terrain (HAAT) is a complicated calculation -so complicated that there’s more than one way to determine what it is, and they don’t always agree. What HAAT really means is “the higher, the better” where your CB antenna is concerned; even a small change in height can achieve a longer range. For example, an antenna on the hood of your vehicle provides a smaller average range than the same antenna mounted on top of the vehicle. It may seem like an additional two or three feet wouldn’t matter, but it does when long-distance communications are the goal.
There’s a reason CB antennas on vehicles always point upwards. While it may be more attractive to lay them flat and make them less conspicuous, doing this will seriously reduce your average range. The longer your wavelength, the less it matters, but it does make a difference.
In an ideal world, the length of your antenna would be the same as your radio wavelength. The Citizen’s Band wavelength is 11 meters or 36 feet, which is quite a tall antenna. To be practical, CB antennas on vehicles are sized to be a fraction of the wavelength. One-eighth, one-quarter, one-half, and five-eighths wavelength antennas are the most common sizes.
One way to make use of a taller antenna is to have a stationary radio setup called a base station CB. The base station can be tied to a mast or tower type of antenna, which gives it more height and therefore a much wider range. A base station antenna can also be considerably larger than one mounted on a vehicle.
Ranked from best to worst, here are the five different types of antennae:
- ¼-wavelength whip antenna: Generally considered the gold standard for range, this is a 102-inch long antenna. Because it’s a straight piece of wire this type is the most efficient in transmitting and receiving 11-meter CB frequencies, so they’re popular with truckers. They are often mounted toward the front of a car or truck, then pulled across and tied down at the back of the car
- Fiberglass antennas: Almost as good as the 1/4-wavelength whips, these have antenna wire coiled around a single fiberglass core, with a weatherproof coating over the entire thing. Many of these are tunable, allowing you to maximize performance on the CB channels you use most. Truckers often use dual fiberglass antennas mounted on the cab for clearer conversations with nearby vehicles
- Magnetic antennas: These can be detached from their magnetic base to prevent theft, or to move them between vehicles. Magnetic antennas are ideal for businesses that have company trucks
- No-ground-plane antennas: Designed for fiberglass boats and other vehicles that don’t have metal surfaces to reflect the radio waves.
- Stubbies: These small antennas are used on handheld CB radios or two-way radios (a.k.a. walkie-talkies). These coiled antennas are only a few inches tall to make them portable, but they have the shortest range
CB radio antennas have to be tuned against what’s called the Standing Wave Ratio, or SWR. Tuning ensures that the maximum amount of RF power goes to the radio antenna. Most modern CB radios have a built-in SWR meter. For older radios that don’t, you can connect an external SWR meter. To learn more about tuning your antenna, be sure to check out How To Tune A CB Antenna.
In order to reach a wider range of frequencies, some CB radios have an additional feature called single-sideband modulation (SSB). SSB radios are usually high-end CB models; they offer more channels, more power, and greater range. Radios equipped with single sideband (SSB) also have an additional control called a “voice lock” or “clarifier” which reduces background noise. The FCC allows 12 watts of transmit power for SSB; however, both the sending and receiving CB radios need to be SSB-capable to communicate on those channels.
While the legal power limit for all CB radios is 4 watts, the actual power delivered to the antenna can vary. Always research the transmitter power output on any radio you consider buying. Some may only have 3.5 watts of power even though the packaging always says “Four Watts”. Handheld CB radios typically have only 2 watts of output, with low-power modes to save battery life.
With a quality antenna mounted on your vehicle or on a stationary mast, your CB radio should be capable of transmitting to at least a seven-mile range. However, depending on the terrain and your equipment, your results will vary. Remember, since the person on the other end has to reach you, too, your equipment needs to have comparable power and range. When shopping for a CB radio, antenna or accessories, choose features that will get the results you want. In the end, these will have more impact on your CB radio experience than anything else.
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