How to Adjust Standing Wave on a CB Antenna

Setup

• 1

  Install your CB and antenna, or have them professionally installed. Have the installation tested for short circuits or continuity problems before checking your SWR.

• 2

  Drive your car or truck to an open area, away from surrounding buildings or trees. Disconnect the antenna cable from your CB, and attach it to the connection marked "Ant" on the SWR meter.

• 3

  Attach your short cable from the SWR meter's other connection to the antenna connection on your CB. Your SWR meter is now inline between your CB and antenna, and can be used to test your standing wave ratio.

Testing

• 4

  Examine the controls on the front of the SWR meter. They vary somewhat from model to model, but there will be a switch that says "Fwd" in one position, and "Ref" or "SWR" in the other. There will also be an adjustable dial or slider, probably labeled "Set" or "Adjust," or something similar.

• 5

  Turn your CB to Channel 1 and flip the switch to "Fwd." Hold down the radio's microphone key, and use the dial or slider to bring the meter's needle to the "Set" position.

• 6

  Flip the switch to the "SWR" position and record the number shown on the gauge, to the nearest 1/10th. For example, if the needle is between the 1.5 mark and the 2.0 mark, you might call it 1.7.

• 7

  Repeat the test, using the CB's Channel 19 and Channel 40. Write down those numbers as well.

• 8

  Proceed to use the CB if all three numbers are below two, as this means that it is properly tuned. If all three numbers are above three, the CB and antenna have not been properly installed and should not be used.

Adjusting Your Antenna's SWR

• 9

  Compare the SWR number for Channel 1 against the number for Channel 40. If the first number is higher, the antenna needs to be electrically longer. If the second number is higher, the antenna needs to be electrically shorter.

• 10

  Shorten your antenna as directed by the manufacturer. Some antennas can be adjusted by screwing their tip further in; others can be lowered by using an Allen key. Most require you to remove the tip and slit the covering, then unwind and remove part of the wire wrapping. Replace the cap and re-test the SWR on Channel 1 until it matches Channel 40.

• 11

  Lengthen your antenna in the same manner, but in reverse. Loosen the adjustable tip on higher-end antennas, or use the Allen key to raise it in its mount. On traditional wire-wound antennas, remove the cap and slide three or more turns of wire further up the antenna. Replace the cap and re-test the SWR on Channel 40 until it matches Channel 1.