To peak and tune a CB radio, connect one end of a coaxial to the antenna input of the radio and the other end to the radio input of a standing wave ratio meter. Connect the CB antenna to the antenna input of the meter. Set the meter to the forward position, turn on the radio, set it to channel 1, depress the talk button on the CB handset, and turn the meter dial until it reads "set."
After completing the "set" step, flip the SWR meter to the "reflect" position, depress the talk button on the handset, write down the numbers and then release the button. Set the CB radio on channel 40 and repeat the "set" and "reflect" steps.
Compare the numbers for channel 1 and channel 40. If the number for channel 1 is higher than that for channel 40, lengthen the antenna. If channel 40 is the higher number, shorten the antenna. Make any adjustments to the antenna in small increments and then retest channels 1 and 40 with the SWR meter. Ideal SWR readings are less than 1.5 on both channels, and the two readings should be as close to each other as possible.
When tuning a CB antenna, the vehicle should be in an open area, away from trees and buildings. Make sure the doors, hood and windows of the vehicle are closed when tuning the radio.