Before attempting any adjustments, review the documentation for your antenna to see how it should be adjusted. A variety of methods are used depending on the type of antenna. Following are general guidelines.
- Check the SWR on channels 1 and 40.If the SWR is lower on channel 1, then the antenna is too long. Make the antenna shorter. If the SWR is lower on channel 40, then the antenna is too short. Make the antenna longer. Continue to adjust the antenna until the SWR is approximately the same on channels 1 & 40 AND is less than 3. The antenna is now properly tuned for the CB band.
To adjust steel whip antennas, loosen the set screw and raise or lower the whip. If necessary, you can cut the antenna to make it shorter (cut in 1/4" increments).
On center-loaded antennas, adjust the length of the top whip.
On fiberglass antennas with no visible means of adjustment, adjust as follows:
Remove the plastic cap from the top of the antenna. Slit the plastic cover to expose the top coils of wire. To lengthen the antenna, pull the top coil up. To shorten the antenna, cut off the top coil. Replace the plastic cap.