How to Modify a Cobra CB Radio


It is illegal to modify the Cobra CB (Citizen Band) radio's circuitry to boost the radio's output. However, you can modify the Cobra CB radio antenna. Modifying a CB radio legally by altering the antenna attached to it will produce notable increases in transmission distances, and will make use of the maximum power that the Cobra can put out. You can modify a Cobra CB radio like this by following a few easy steps.

  • Attach the Cobra antenna to the CB radio, and extend the antenna fully by loosening the set screw that you'll see on the mast. Loosen it just so that when you tap the top of the antenna mast, the mast length adjusts. The mast length is modifiable like this and the changeable length tunes the antenna.

  • Select Channel 21 on the Cobra radio. Channel 21 is the mid-most channel that the Cobra uses.

  • Take a look at the SWR meter on the front of the Cobra radio and tap the mast, making it shorter. The SWR meter will indicate a lower reading whenever you tap the mast. Keep tapping until the SWR mater gets to its bottom-most point and begins to rise. At this point, the antenna is tuned for Channel 21 and will provide best results for Channel 21.

  • Select channels from 1, the lowest, to 40, the highest, and verify that the results are similar. The Cobra CB antenna is now modified so that it provides optimum signal and power for the radio.


  • Photo Credit routier image by ninice64 from
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