How to Tune a CB Antenna

Don't underestimate the importance of tuning a CB antenna. Some CB antenna manufacturers include instructions that say, "For optimal performance, you may need to tune the antenna using an SWR meter." What they don't say is that if you fail to tune your CB antenna, you can actually overload your CB radio, burning out sensitive electronics and ruining it. In order to ensure your CB radio functions properly and won't burn out, tune your CB antenna with an SWR meter, even if it's a pretuned antenna.

Standing-Wave Ratio
Standing-wave ratio is the reason you need to tune your antenna. Without getting into too much technical detail, your radio puts out power, but an out-of-tune antenna reflects some of that power back to the radio. If too much power comes back down the feedline into the CB, you can eventually overload the amplifier in your radio. When you tune the antenna, the SWR meter tells you how close you are to disbursing most of the energy that your CB radio produces. Depending on your specific setup, a high SWR may indicate that you need to lengthen or shorten your antenna.

Preparing to Tune Yyour CB Antenna
You'll need to hook your SWR meter into the line between your antenna and your CB radio. The easiest spot to hook in the SWR meter is right after the radio. Before you use your SWR meter to tune your antenna, make sure you're at least 10 yards from big buildings, other cars and trees. Close all your doors and the trunk of your vehicle. Once you're properly set up, you can use the SWR meter to tune your antenna.


Using the SWR Meter
Set the meter to FWD. Turn the CB to Channel 1 and key the microphone. Adjust the SET knob to get the needle into the "full" range. You've just calibrated the SWR meter for your setup, so now you can move the switch from FWD to REF.

Once your SWR meter is calibrated and you're in REF mode, key the microphone again at Channel 1. Record this number. Switch to Channel 40 and key the microphone again. Record that number. That's your SWR. Ideally, your SWR would be 1:1. As long as you get your SWR under 1.4:1, you're not in danger of ruining your CB radio and your performance should be fine.

CB Antenna Length
When you compare your SWR readings, a higher SWR on Channel 40 than on Channel 1 tells you that your antenna is too long. A higher SWR on Channel 1 than on Channel 40 means your antenna is too short. Tunable-tip antennas make it easy to adjust the length with a simple locking mechanism to lengthen or shorten your antenna. If you've got a fiberglass antenna, follow the manufacturer's instructions to shorten the CB it. Err on the side of cutting too little rather than too much, as you can always shorten the antenna further to reach your ideal tuning.

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