CB radio range that you can expect is probably one of the earliest questions people ask about when getting into Citizen’s Band Radio. I was no exception and have always been fascinated by getting the maximum out of any radio gear.
What many don’t realise is there are many factors that can affect how many miles can a CB radio transmit.
So, How Many Miles Can a CB Radio Transmit?
The rough answer is that between 2 and 20 miles plus is fairly typical of most set-ups. However, you really need to know the factors that will squeeze as much as possible out of your setup.
Plus, there is something else that you should be aware of that could put hundreds if not thousands of miles on your CB radio’s range. So read on.
What Affects CB Radio Range?
We can separate the things that can affect how far you can reach on a CB into the three following classifications; Radio Related, Antenna and your Location / surroundings.
Radio Variables
Power
In general, there is a direct relationship between the power output of a CB radio and its transmit distance. This means that as you increase the power output, you can expect to achieve a longer transmission range.
However, this isn’t as exciting or achievable as it sounds.
While more power equals a greater distance. However, you do have to double your power to gain one S-point on the meter. It’s an uphill battle that gets hard (and expensive) very quickly.
The legal maximum power output is 4 watts anyway so that’s what we are stuck with.
Mode
While AM (and now also FM) tend to be the standard for CB radios and is great for local communication. SSB signals on the other hand tend to travel further. This can often be tens of miles under normal conditions. It works even better under skip conditions and is often the mode of choice for DX work.
Interference
Noise, whether it comes from your vehicle ignition or sources around the house (including Broadband, Wi-Fi routers and cell phones) a high noise floor can serious affect the distant signals you can hear.
Installation Quality
We’ll mention this more under antennas but low SWR (Standing Wave Ratio) is really important. High SWR leads to significant power that isn’t radiating out of the antenna. Not to mention can damage your radio.
Cheap coax cables can lead to significant power loss especially over long runs. The same can be said of connectors that should be properly soldered.
Atmospheric Conditions
Range of a CB can also be affected by weather / atmospheric conditions.
However, it isn’t all bad. Under certain conditions, such as during skip propagation, radio signals can bounce off the Earth’s ionosphere and travel much farther than usual. However, this phenomenon is sporadic and not something that can be controlled through power adjustment.
Antenna Variables
Your CB antenna and how it is set up can have a massive influence on your maximum range.
SWR (Standing Wave Ratio) Tuning
It’s essential to tune your CB antenna using an SWR meter to achieve the best possible performance. A high SWR reading indicates poor antenna matching and can lead to decreased range and potential damage to your CB radio. Proper tuning ensures that your radio is transmitting efficiently.
Physical Length
Shorter antennas rarely work as well. Ideally you want a quarter wave or half wave which equates to roughly 9 feet or 18 feet respectively.
This is obviously not possible in mobile installations and coils are used to maintain the electrical length while restricting the physical length.
Physical Height
The location where you mount your CB antenna has a significant impact on its performance. Ideally, the antenna should be mounted as high as possible to achieve the best range.
Home base antennas are much easier to mount high with vehicles having obvious limitations. A truck does have a slight advantage over a car though.
Location / Surroundings
A CB radio’s average range is seriously affected by where you are located.
Terrain and Obstacles
CB relies on line-of-sight for local communication (for distance see the Propagation / Skip section). This means that for optimal range, there should be a clear, unobstructed path between the transmitting and receiving antennas. Buildings, hills, trees, and other obstacles can block or reflect radio waves, reducing the effective range.
Handheld / Portable CB Radio Range
Handheld CB radio can be quite restricted in terms of range with 1 to 3 miles being typical. This limitation is primarily due to three factors.
Power Output
Handheld CB radios typically have a lower power output compared to vehicle-mounted units. However, now that battery technology is much better many more full power (4 Watt) handhelds around.
Antenna
Longer, telescopic antennas perform better but I prone to damage especially when retracted without care (don’t push down from the tip).
Rubber ducks are more convenient but will seriously hamper your range. They are worse because the physical size is limited due to the coil inside it.
Height
As mentioned before height is an issue and a handheld antenna is going to be pretty close to the ground. However, being portable you can at least move away from objects and obstructions.
We discuss more about walkie talkie range here.
How Do I Maximize My CB Radio Range?
I was no exception and have always been fascinated by getting the maximum out of any radio gear. Improving the range of a CB is quite a fun part of the hobby for me and very satisfying.
Improve Your SWR
I always make sure I get my SWR as low as possible. While it is recommended that you get it to 2:1 or lower. At 2.0:1 you will lose around 11% of the power. Or rather than much gets reflected back into the radio. At 1.1:1 you lose just 0.3% of your power.
Use Quality Coax
Poor grade coax can lead to quite big power losses, particularly over long runs. If you are using a base station CB then make sure you use the thick stuff.
Better Antenna
Longer antennas generally perform better. For motor vehicles go for the longest whip or fiberglass antenna that will fit comfortably on your vehicle.
With a base station antenna use a decent quality one that’s at least a half wave, ¾ wave or 5/8 wave.
Top brands include:
Mobile: Wilson, K40, Firestik
Base Antennas: Maco, Hustler, Solarcon, Sirio
Higher Antenna
The best you are going to achieve on a car is a magnetic mount in the middle of the roof. At least though you can drive to a higher location.
If you are running a base station CB then a decent height is obviously much easier to achieve. Well, if HOA rules don’t affect you.
Use SSB
Single Sideband (SSB) mode is far more effective for distance work. The Federal Communications Commission (FCC) allow 12 Watts output power for SSB.
This increased effectiveness is due to several key factors:
- Efficiency of Spectrum Usage:
- SSB transmits only one sideband of the audio signal, eliminating the carrier and the other sideband, which are transmitted in AM. This results in a significant reduction in the bandwidth required for transmission.
- AM uses a lot of bandwidth to transmit the carrier and both sidebands, making it less spectrum-efficient. SSB, on the other hand, uses the available spectrum more efficiently, allowing for more channels in the same frequency band.
- Reduced Interference:
- Because SSB transmissions are narrower in bandwidth, they are less susceptible to interference from adjacent channels and atmospheric noise. This makes SSB more reliable for long-distance communication where signal quality can be a challenge.
- Increased Power Efficiency:
- SSB radios can allocate more power to the single sideband being transmitted compared to AM radios, where power is divided between the carrier and both sidebands. This results in a more powerful and effective signal for long-distance communication.
- Improved Signal-to-Noise Ratio:
- SSB signals are less affected by noise and interference due to their narrower bandwidth and reduced vulnerability to atmospheric conditions. This leads to a higher signal-to-noise ratio, making it easier to hear distant stations.
Quality SSB radios include: Galaxy DX-959, Uniden BEARCAT 980SSB, PRESIDENT MCKINLEY
Address Interference Issues
When you encounter interference, it’s like trying to have a clear conversation in a noisy room—it becomes difficult to hear and understand incoming signals. Addressing interference issues is crucial if you want to maximize your CB radio’s reception range.
- Reduce Electrical Noise: Electrical noise from various sources, such as engines, alternators, or power lines, can disrupt CB radio reception. To mitigate this, ensure that your CB radio’s power source is well-filtered and free from electrical noise. Use quality power cables and consider installing noise filters to reduce interference.
- Choose a Low-Noise Location: When installing your CB radio and antenna, select a location that minimizes local interference sources. Avoid mounting antennas near sources of electrical noise or in close proximity to metal structures that can reflect or block radio waves.
- Properly Ground Your Equipment: A good ground connection is essential for reducing interference and enhancing reception. Ensure that both your CB radio and antenna have proper grounding to help dissipate unwanted electrical noise.
- Use Noise Blankers and Filters: Many CB radios come equipped with noise blankers and filters that can help suppress interference. These features can be effective in improving the clarity of received signals, especially when dealing with nearby sources of interference.
- Antenna Height and Placement: We are back onto height but it’s important to know that the height and placement of your CB antenna play a crucial role in minimizing interference too. Elevating the antenna above nearby obstacles can help reduce interference caused by terrain or buildings.
Propagation / Skip
This is the magic that can significantly add to the range of a CB radio. “Propagation” or “Skip” is a phenomenon that makes CB radio communication absolutely amazing. It can allow signals to travel far beyond line-of-sight.
Propagation, in the context of radio, refers to the way radio waves can bounce, refract, or diffract off various layers of the Earth’s atmosphere.
Under ideal conditions, signals can cover vast distances, sometimes even spanning hundreds or thousands of miles, making it possible for CB operators to communicate across countries or even to other continents.
The mechanism behind this long-distance reach is a bit like a game of billiards in the sky. When a CB radio signal is transmitted, it travels upward into the atmosphere. There, it can encounter layers of charged particles or electrons, known as the ionosphere, which act as a sort of mirror for radio waves.
These layers can reflect the signal back towards Earth, where it bounces off the surface and returns to the ionosphere. This process can repeat several times, creating a skip pattern, with the signal “skipping” off the Earth’s surface and the ionosphere multiple times before reaching its destination.
What’s fascinating is that skip propagation can occur during certain atmospheric conditions, often influenced by factors like sunspots, solar flares, and the time of day. These variables can affect the ionosphere’s density and create favorable conditions for long-distance skip propagation.
This distance work is often referred to as DX. Part of its appeal is also its downside as skip is unpredictable and bother seasonal and affected by the time of day.
Low Angle of Radiation
A low angle of radiation from the antenna is a desirable characteristic to achieve the greatest distances.
This is where a ground mounted antenna can come in useful because signals coming off of it have a much lower angle of radiation. This is counter-intuitive and rubbish for local communication.
However, it is common practice in amateur radio. A ground mounted antenna is often used for distance work. The key is to use lots of radials – it makes a massive difference.
Conclusion
We’ve seen there are multiple factors that can influence the performance we get from our CB radios. Fortunately, we have control over them and with a little effort we can increase our maximum range.