General Troubleshooting
Antennas and Coax

  • SWR that pegs the needle on all channels almost always indicates a short in the antenna system. Do not attempt to tune the antenna until the short is fixed.
  • SWR that is high on all channels (over 2:1 but not pegging the needle) after the antenna has been tuned usually indicates a coax or ground plane problem.

Proper Stud mount assembly

Make sure plastic insulator is on the top

Coax for single antenna vs dual antenna systems.

Single antenna installations can use any length of 50 ohm coax to work properly. You only need enough coax to get from the radio to the antenna. If you end up with extra and need to coil it up, make sure you have the coil diameter 12" or larger.

Dual antenna installations require a different kind of coax that is designed to mate two 50 ohm antennas together. When connecting two 50 ohm CB antennas you get 25 ohms which would give you a 2:1 SWR mismatch. The "special" coax used to correct this is 75 ohm coax cut to a specific length acting as a matching circuit. The length is 1/4 wavelength on 11 meters times the velocity factor of your coax. A quarter wavelength in the middle of the CB band is around 8.6'. Velocity factor varies but for this example we are going to use a .69 VF. So 8.6' x .69 VF equals 5.93 feet. This is physically too short for most installations but fortunately you can use odd multiples of the 1/4 wavelength (1,3,5, etc). For most installations a 3/4 wavelength works perfectly. (5.93 x 3 = 17.8') Circuit Master stocks custom phasing harness's with proper connectors ready to go for dual antenna installations.