Once you have installed your CB radio and antenna, you need to tune the antenna, known as the SWR setting.
Why Tune The Antenna?
Tuning the antenna is the most important step in the CB radio system installation to make sure that it is performing its best. CB radios come with 4 watts of power only, so you need to get your antenna system working efficiently to maximize the radio transmission and reception.
The antenna if poorly tuned can lead to increased interference, lack of ability to make the best quality contact, dropped signals, and even damage the radio.
Is There A Difference Between Tuning CB Radio And Tuning The CB Antenna?
Tuning a CB radio is different from tuning the antenna. CB radio can be tuned to increase performance also. The new radio is tested, the power is adjusted and the modulation is done with the aim to make the radio sound as good as possible.
A common misconception is that the antenna is being tuned to the radio. How to peak and tune a CB radio involves adjusting the actual radio, not the antenna. Tuning a CB antenna is tuning the antenna to the vehicle or application and not to the radio.
What Is Tuning A CB Antenna?
Tuning the radio system is to adjust the antenna to the correct height so that the radio puts out signals efficiently. This varies according to the vehicle or application, the location where the antenna is installed, the ground plane, and more.
Firstly, measure how the system is performing currently with an SWR meter, then you adjust antenna length for the location so that the signal is improved. Citizen band antenna tuning means trying to get the lowest SWR reading possible.
That is done by increasing or decreasing the length of the antenna in very small increments of 1/4th inch or less, then testing it again. That gives you the best performance and transmission efficiency.
Your radio can be excellent but without proper tuning of the antenna, it will be like having a boat anchor installed in the vehicle. So tuning of the antenna is important for the overall performance of the system.
What Is SWR?
SWR means standing wave ratio. A SWR meter is used to measure how well the transmit power signal emitted from a transceiver is traveling through the system into the atmosphere. To check and set the antenna is critical to the overall performance of the transceiver.
During the installation of a business band, CB, Marine, or Ham radio or installation of a new antenna, the SWR is to be checked to make sure that transmit power coming from the radio travels through the antenna system correctly. A poor performing system reduces range and damages the transceiver.
When the signal does not travel properly through the antenna system, the transmit power reflects back into the transceiver causing reduced range and damage to the internal parts of the radio.
How To Tune A CB Radio With A Built-In SWR Meter?
The SWR meter is used in conjunction with short coax cable between the antenna system and the radio to perform the test. High reading on the SWR meter indicates that there is a problem with the installation of the radio or antenna system.
When the test is performed for the meter, indicates if the antenna is working properly and provides reading so the antenna can be adjusted for better performance.
The SWR readings indicate if there is a poor or bad ground, poor antenna location, improperly set antenna or coax obstruction, or short. Reading on the SWR meter indicates that there is a problem with the antenna system or a bad ground that needs correcting or adjusting before using the radio. Do not operate the radio until you achieve a good SWR.
CB radio SWR meters 26 – 27 MHz are inexpensive, such as AUSWR. Meters used to check other radio frequencies may be expensive. Purchase the SWR meter that tests the frequency range your radio operates IN.
For example- CB radios operate on 26 – 27 MHz whereas Marine radio operates on 156 – 164MHz. A short coaxial cable with two PL259 connectors like the PP8X1 is needed in conjunction with the SWR meter to perform the test.
When you buy an SWR meter, you have to order a coaxial cable separately if it is not included with the meter. Checking and setting the SWR on all radio applications is important to obtain the best performance possible.
When you test and adjust the antenna, make sure to check SWR on the lowest channel and the highest channel by registering and setting the SWR on the entire bandwidth, it ensures optimum performance on all the radio channels.
The radio receives and transmits with SWR reading of 2.5 or less on all channels, the lower the SWR reading the better your radio will perform.
The SWR reading shows how much of the radios’ power is turned into radio signals by the antenna. If the SWR reading of 1.0 indicates that a hundred percent of the radio’s power is being transmitted.
The ratio of 3.0 is registered when the antenna transmits a third of the radio’s power. It indicates a poorly tuned antenna that does not allow the signal to travel through the antenna system properly.
The transmit power is reflected back into the radio through the coaxial cable, causing reduced function. If too much power is reflected back, the internal parts of the radio may be damaged due to increased heat generation.
To avoid damage, keep the SWR levels below 2.0, the level of 3.0 or more could indicate a serious problem. If you know that you will operate your radio on Channel 40 only and you are getting a good SWR reading on 40 but a bad reading on CHANNEL 1 you should operate a radio on Channel 40 but do not operate on the channels with bad readings.
How CanThe AntennaLength Be Adjusted?
It depends on the type of antenna you are having. Some Antennas provide easy tune options, some are not quite as easy to tune and may require to trim the Steel whip or trim wires inside of the antenna.
The antenna manufacturers should provide instructions to explain how to adjust the antenna. Some antennas contain a tuning tip, a small screw at the top of the antenna like the Firestik.
To adjust the antenna you have to turn the screw in or out easily shortening or lengthening the antenna.
For other antennas that do not have this tuning tip, you can shorten the antenna by cutting off a very small portion of the tip at a time. Another option is to adjust the length of the coax for adding or removing additional items in the antenna system like quick disconnects and springs.
How To Tune CB Antenna Without SWR Meter?
To tune a CB antenna, it requires nothing more than your installed radio antenna, coaxes, and SWR meter. Begin with choosing an appropriate location to do the tuning, move on to connecting the SWR meter. Then be ready to start actually tuning the antenna with the step-by-step instructions given below.
Choosing The SWR Testing Location
You want to place your vehicle in an open area when tuning your CB antenna. Tuning the antenna when you are very close to other vehicles, buildings or people can give you an incorrect reading.
Each time you take the reading, make sure your doors Windows and Hood are closed. If your antenna has a plastic cap on the tip, make sure that it is in place each time you take a reading.
How To Connect An External SWR Meter?
Some CB radios come with a built-in meter. The owner’s manual includes step-by-step directions for the operation of the built-in meter. If a CB radio does not have a built-in SWR meter, you need to get one.
The AUSWR SWR meter is affordable and comes with coax jumper cable which you require to connect the meter to your CB radio.
The AUSWR SWR meter is a popular choice if the CB radio does not come with a built-in meter. Other SWR meters are available, and some have additional meters.
How To Tune A CB Antenna Using AUSWR External Meter?
Turn the Citizen Band off and disconnect the antenna coax cable from the back of the radio.
Connect the end of the antenna coax to the SWR meter where it is showing ” antenna” or “ANT”. The connector inputs may be on the back and the labels on the front of the meter.
Connect the short coax jumper cable coming from the transmitter position to the SWR meter on the back of the CB.
Close the doors and hood on your vehicle, and make sure that there are no other large vehicles or people around the vehicle area.
Turn on the CB
Set the CB to channel 40
Set the SWR meter to the forward position.
Key the microphone by depressing the talk button and turn knob until the SWR meter indicates the set position. Unkey the microphone by letting up on the talk button. Be careful because many meters have both and SWR and RF power scale so be sure to read the SWR reading.
Flip the SWR meter to the ” REF” (reflect) position
Key the microphone and look at the reading on the SWR meter for channel 40.
Repeat steps 6 through 10, on Channel 1.
The lower the reading on the SWR, the better the CB radio will perform. The aim is to set the antenna to the lowest SWR readings possible, evenly across the 40 channels. For example, reading on Channel 1 and 40 are the same at 1.5. By having the same readings on Channel 1 and 40 the radio will perform well on any of the channels within the bandwidth. If they do not match, adjust the antenna.
If the meter reading is in the red zone, showing higher SWR readings, do not operate the CB. You may damage the radio.
If the reading on Channel 1 is higher than that on Channel 40, the antenna system is too short and you have to lengthen your antenna.
If the SWR meter reading on Channel 1 is 2.6 and on Channel 40 is 1.3, your antenna is too short. You need to increase the physical length of the antenna system. Add spring for quick disconnect, raising the antenna, get longer coax, or reposition the antenna.
If the reading on channel 40 is higher than Channel 1, the antenna system is too long and you have to shorten your antenna system.
If the SWR meter reading on Channel 1 is 1.2 and on Channel 40 is 2.3, the antenna is too long. You need to shorten the antenna system to get better efficiency. You can do that by turning the tuning tips for adjusting the ring or take the antenna mast out and trim at about 1/ 8 inch and place it back firmly against the coil. It is easier to cut a little more of the antenna than to add some length.
SWR range explanations
SWR 1.0 – 1.5: if your SWR is under 1.5 you are in great shape. If you want to drop down to closer to 1, it’s possible to do with additional tuning, different equipment, or different mounting location. But the drop from 1.5 to 1.0 will not make a substantial increase in performance. It’s not as noticeable as going from 2.0 down to 1.5.
SWR 1.5 – 1.9: SWR in this range still provides adequate performance. Due to installation, vehicle variables it is impossible to get SWR lower than this. Try to get it lower but performance should be acceptable in this range. If you have tuned the antenna SWR in this range is likely an issue of less than the ideal mounting location of the vehicle and an antenna that is not ideal for the mounting location.
SWR 2.0 – 2.4: this won’t damage your radio with casual use, although it is not good. You should try to improve it if you can. This range is caused by poor antenna mounting location and a poor choice of equipment for the specific vehicle. For troubleshooting, you need to move the mounting location or use a more suitable antenna. It is not a good tuning job but will function if you have exhausted all the other possibilities of troubleshooting.
SWR 2.5 – 2.9: performance in this range will be decreased and you may even damage or radio if you transmit frequency for extended periods. You should not operate your radio in this range. This range is caused by the poor mounting location or poor choice of equipment for the specific vehicle. To troubleshoot you need to move the mounting location or use a more suitable antenna.
SWR 3.0+: in this range, the performance will be severely affected, you would damage the radio with extended transmission use. You should not transmit your CB at SWR levels above 3.0. If the SWR needle swings to the right when getting your 3.0 + readings, you certainly have a major installation problem. This is the result of poor ground or improperly assembled stud, but rarely it indicates a faulty coax antenna or incorrectly attached SWR meter.