Antenna length is directly related to signal frequency. Therefore, it must be tuned to resonate optimally throughout the frequency range of the transceiver. Lower frequencies require a longer antenna than higher frequencies. Due to the various methods of adjusting antennas for proper SWR, we have chosen what we think is the optimum method:
Antennas with adjustable screws (set screws)
- Start with the antenna extended and tighten the set screw lightly enough so that the antenna can be lightly tapped with your finger for easy adjustment.
- Set your radio to your desired operating frequency or the center of the range of frequencies you plan to use. Press the PTT (Press-To-Talk) switch, and tap the antenna (making it shorter). The SWR meter will show a lower reading each time the antenna is tapped. By continuing to shorten the CB antenna, you will notice the SWR reading will reach a low point and then start rising again. This means that you have passed the optimum point for the middle frequency.
- Extend the antenna a short distance and again follow the procedure above.
- When the lowest point has been reached, switch to the lowest frequency you plan to operate on and then to the highest and compare SWR readings. They should be almost equal.
Antennas that must be cut to proper length.
- Follow the procedure as in “A” above, but adjust the length by cutting in 1∕8″ increments until a good match is obtained.
- Be very careful not to cut too much off the CB antenna at one time. Once it is cut, it can no longer be lengthened
- The whip is easily cut by filing a notch all the way around, then breaking the piece off with pliers.
NOTE: The proper setting is achieved when the SWR is 1.5 or below and when it has the same reading for the low and high frequencies in the range you plan to use.
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