Antennas that only receive signals don't require matching, but CB antennas must send and receive. Antennas come pretuned, but once you install the CB in your vehicle, the vehicle's body, by reflecting the signal back at the antenna, becomes part of the tranmission process. No matter how well the manufacturer pretuned the antenna, it may perform differently depending where you position it on the car. Once the antenna is in place, begin matching to give it the best signal.
A CB antenna matcher is another name for a Standing Wave Ratio (SWR) Meter.
The meter matches the length of your radio antenna to the wavelength it's transmitting on. Matching or tuning the antenna correctly guarantees the strongest signal and also ensures your radio uses power efficiently.
The Standing Wave Ratio measures how much of your CB radio's power is turned into radio signals. At an SWR of 1.0, the transmission uses 100 percent of the radio's power. At 3.0, only a third of the power goes through. Not only do higher readings mean a weaker signal, but the unused power radiates out of the CB as heat. The higher the ratio, the greater the heat: Above 3.0, it's hot enough to damage your CB.
SWR matchers contains a meter, a dial and a switch labeled "FWD" and either "REF" or "SWR." To match your antenna, park the car with 15 meters of open space around it and connect the matcher to your CB radio and antenna. Set the matcher to FWD, switch the radio to Channel 1, and press down the radio's "Talk" button. Turn the SWR dial until the meter reaches "Set." Flip the switch and record the numerical reading. Repeat the process with Channel 40.
If Channel 1 has a higher SWR, your antenna needs shortening; if Channel 40 is higher, it needs lengthening. Adjust the antenna slightly, then take a new reading. Keep going until the ratio for both channels is below 2.0, and the two ratios are as close to identical as possible. This produces the strongest signals on any of the 40 CB radio channels. Depending on your antenna model, you adjust it by loosening a screw at the tip, or by sliding a steel whip in or out of the base.
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