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different antenna for different frequency

How to Tune Dual CB Antennas (Step-by-Step Guide)

Updated On May 20, 2022

Tuning the antenna is the most crucial step in dual CB antenna installations. It ensures that your CB radio system performs to its full potential. Also, it will improve the system’s overall functionality and assist in guaranteeing that you do not harm your radio and avoid poor broadcast signals.

In general, with your SWR meter, you can tune your dual CB radio antenna with these steps: 

  • Remove the antenna coax cable from your radio’s rear. 
  • Connect the antenna coax’s end to the meter’s “ANT” indicator, and connect the short coax jumper cable from the meter’s “transmitter” position to the CB’s back. 
  • Switch on the CB, select channel 1, and set your SWR meter to its FWD position.
  • Key the microphone and spin the knob until the SWR meter indicates its “set” position.
  • Switch the meter to its “REF” or “SWR” position, then repeat the process on channel 40.

In this guide, let me show you a more detailed process of tuning your dual CB antenna and discuss the possible SWR meter results.

Steps to Tune the Dual CB Antenna using SWR Meter 

So, how do you tune dual CB antennas? Tuning your dual CB radio antenna isn’t difficult if you follow our instructions and are willing to experiment. Here are the steps:

Step 1: Finding a decent parking spot. There should be no obstacles within 10 to 15 meters of your antenna CB radio, such as trees or buildings. Then, close your vehicle’s hood and doors, and ensure no people or large cars are nearby to get a correct reading.

Step 2: Turn off your CB and remove the antenna coax cable from your radio’s rear.

Step 3: Connect the antenna coax’s end to the SWR meter’s “antenna” or “ANT” indicator. The connection inputs may be on the meter’s back, while the labels may be on the front.

Step 4: Connect the short coax jumper cable from the SWR meter’s “transmitter” or “XMIT” position to the back of the CB where the coax line was removed in step 2.

connecting the short coax jumper cable from the SWR meter
Video | Jerry Arbs

Now you may test the SWR on several different channels. Remember to keep the microphone at the same distance from the meter throughout the operation.

Step 5: Switch on the CB and select channel 1.

Step 6: Set your SWR meter to its FWD (forward) position.

setting SWR meter to forward position
Video | Jerry Arbs

Step 7: Key the microphone. To do it, depress the talk button and hold it. Then, spin the knob until the SWR meter indicates its “set” position.

Step 8: Switch the SWR meter to its “REF” or “SWR” position while still keying the microphone.

switching SWR meter to "REF" or "SWR"
Video | Jerry Arbs

Step 9: Quickly record the reading from your SWR meter and release the broadcast key on your microphone.

Step 10: Then, repeat steps 5 to 9, but this time on channel 40.

SWR Meter Results on CB Antenna Installations

The lower the SWR meter reading, the better the performance of your CB radio. The idea is to configure your dual antenna to the lowest possible SWR readings, uniformly distributed throughout the 40 channels.

With that, your radio will function well on any of the channels within the 40-channel bandwidth. If they don’t match, you should adjust the antenna CB radio. (1)

Here are the possible scenarios:

1. Channel 1 Reading is Higher than Channel 40

It means that your dual CB antenna is too short. For example, channel 1’s SWR meter reading is 2.6, while channel 40 is 1.3. In that case, you’ll need to lengthen your CB antenna set up physically. Adding a spring or quick disconnect, lifting the antenna, getting longer wire, or re-positioning the antenna are all possible solutions. You should have that equipment cited on your CB antenna kit.

2. Channel 40 Reading is Higher than Channel 1 

It means that your dual CB antenna is too long. For example, channel 1’s SWR meter reading is 1.2, but channel 40 is 2.3. You’ll need to shorten your CB antenna setup to improve efficiency in that scenario. You can accomplish that by turning the tuning tip or adjusting the ring, or you can remove the antenna mast and trim it down to about 1/8 inch, then firmly reinstall it against the coil. Thus, it would be best to have that equipment on your CB antenna kit. (2)

Now, because you’re tuning a dual antenna, make sure you adjust both antennas simultaneously. First, turn the tuning screw in or out so that each antenna is the same length. After that, lengthen or shorten both antennas by the same amount each time, based on your SWR readings. Then, re-measure SWR and modify it as if it were a single antenna, making incremental modifications as close to both antennas as possible.

Caution: Do not use your CB if the meter reading is in the red zone, which indicates HIGH SWR readings. In that case, there’s a high chance your radio could be damaged. 

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References
(1) bandwidth – https://www.techtarget.com/searchnetworking/definition/bandwidth
(2) improve effeciency – https://www.indeed.com/career-advice/career-development/strategies-to-improve-work-efficiency

Video Reference

About the author 

John Temple