How to Increase Power Output on Cobra CB Radios

by Patrick Nelson

The Federal Communication Commission (FCC) limits the maximum power a CB radio can transmit at 4 watts. You legally can't boost the radio's power. However, power from the Cobra radio isn't the only factor involved in transmitting distance. The antenna can be tuned to allow the maximum power to be transmitted. In effect, increasing the power output of the Cobra.

Step 1

Extend the antenna and tighten the set screw lightly. The antenna should be able to be tapped with your finger to adjust the length.

Step 2

Set the Cobra CB to channel 21.

Step 3

Press the push-to-talk (PTT) switch and tap the antenna, making it shorter. The SWR meter will show a lower reading each time the antenna is tapped.

Step 4

Keep tapping until the SWR meter reaches its lowest point and starts to rise again. The lowest point is where the antenna is optimized for channel 21.

Switch between channels 1 and 40 and compare readings. They should be very similar. The antenna is now optimized to provide the maximum power output.


  • Some tunable antennas can be cut, rather than adjusted. Cut the antenna length in eighth-of-an-inch increments. Obviously, don't cut too much as you won't be able to lengthen it if you have to.


  • Keep all doors closed when adjusting the antenna. Check you don't pinch your coaxial cable

Items you will need

  • Cobra CB radio with a built-in SWR meter
  • Mobile adjustable antenna with adjustable screws

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