FCC regulations allow CB radio users to broadcast with a power of 4 watts or less. This makes tuning your antenna essential in order to make sure that maximum power is being transmitted by your antenna, and to keep your CB radio usage trouble-free for years to come.
Standing Wave Ratio
Tuning a CB antenna means adjusting it so that the maximum amount of power is transmitted from the radio -- you need this maximum power for transmitting over longer distances. The success of a tune is measured through something called Standing Wave Ratio, or SWR, which is the ratio of power transmitted out from the antenna versus what is transmitted back to the radio. A “perfect tune” has an SWR of 1:1 when measured by an SWR meter.
The goal of a tune is to get the SWR to as close to 1:1 as possible, although anything under 1.5:1 is good enough to transmit with. SWR readings of up to 2:1 are safe, although not optimal. Once the SWR reading rises above 3:1, operating the radio becomes dangerous because the reflected power returns to the radio in the form of heat.
Heat reflected back to your radio due to an untuned antenna can damage the radio's internal components. In addition, many CB radio manufacturers will not repair radios found to be damaged due to improper tuning. Even a slightly out-of-tune antenna can cause problems, though mainly in the form of lower power output than intended.
Check the SWR readings on both Channels 1 and 40 with the SWR meter when tuning an antenna. This gives a more accurate representation of your antenna's performance. You want an SWR reading of 1.5:1 or less on both channels. If the SWR reading on Channel 1 is higher than the reading on Channel 40, your CB antenna is too short; if the opposite is the case, your antenna is too long.
Make small changes and check the SWR readings after each change when attempting to tune your antenna. This will prevent you from possibly shortening your antenna too much, or vice versa. Also check your coaxial cable connections, as improper ones can cause high SWR. There should be no fraying, kinks or sharp bends in the cabling. Finally, ensure that your radio is properly grounded by following the radio manufacturer's directions.
- Photo Credit Comstock/Comstock/Getty Images