For optimal performance, a CB radio antenna should be tuned using a SWR matcher or meter. The meter measures the standing wave ratio between the antenna and the radio. The radio can transmit at maximum power when this ratio is below 2:1. If your CB radio SWR is significantly above this level, it should not be operated until the antenna system is fixed. Match your CB system to avoid poor performance and possible electrical damage.
Test and adjust the antenna system for continuity using a multimeter. Drive your car to an open area, and keep the doors closed during testing. Leave the rubber weather cap on the tip of the antenna during the antenna matching procedure.
Connect the CB radio antenna jack to the transmitter terminal on the SWR meter using the patch cable. Connect the antenna cable to the antenna terminal on the SWR meter.
Turn the SWR meter on. Flip the switch on the meter to "FWD," and turn the radio to channel 1. Press and hold the transmit button on the CB handset, and turn the "Set" knob of the meter until the needle reading is in line with the set mark. Flip the switch to "REF" or "SWR" and record the needle reading to one decimal place.
Flip the switch back to "FWD," and turn the radio to channel 40. Perform the same procedure, recording the needle reading for this channel.
Adjust the antenna according to the meter readings. If the reading on channel 1 was greater than channel 40, then the antenna is short. Lengthen the antenna by turning the tip screw or by extending the whip. If the reading on channel 40 was greater than channel 1, then the antenna is long. Shorten the antenna by turning the tip screw, retracting the whip or clipping a small length of the tip with wire cutters.
Tune the antenna until the readings on channel 1 and channel 40 are below 2.0 and are close to matching.
If the SWR readings are greater than 3.0, the antenna system may have continuity or grounding problems.