Tuning your CB antenna/antennas using an SWR meter is pretty simple and is absolutely essential.
Failure to properly tune your CB antenna/antennas can damage your CB Radio. Failure to tune can also limit your transmittal and reception strengths. A properly tuned CB Radio system is a happy CB Radio system.
Learn to properly use an SWR meter and after your initial set up you should check your SWR once a month. Road and weather conditions can and will over time change your SWR.
Materials needed:
- An SWR meter
- A 3 foot section of coax cable
1. Disconnect the antenna cable from the back of the CB Radio. Connect the antenna cable to the coax antenna in-put on the back of the SWR meter. Use the 3 foot section of coax cable to connect the SWR meter coax antenna out-put to the CB Radio. ** On the SWR meter there should be several switches. These are: “REF” or “SWR”, “FWD” and “Set” or “Adjust”
2: Tune your CB Radio to channel 1(one) and set the SWR meter switch in the Forward “FWD” position. Hold the CB in transmit mode by pressing the PTT button on the mic. Ajust the SWR meter needle using the Set or Ajust knob on the meter until the needle is in alignment with the corresponding mark on the meter. Flip the switch to the Reference “REF” position. The meter is now showing your SWR on channel one. Take note of the value and quickly release the mic PTT button.
3: You will need to repeat step 2 on channel 19 & 40. Make sure you’re taking notes,
you’re gonna need them.
Reading the SWR Meter Results & Knowing What They Mean:
With an SWR reading of less than 2.0 on all three channels (1, 19 & 40) the CB Radio can be safely operated.
If the SWR meter is in the “Red Zone” on all three channels (1, 19 & 40), there is likely an electrical short in the coax antenna cable, connectors or the mounting stud was installed incorrectly. This may damage the CB Radio, do not operate the CB Radio until the problem is resolved.
If the SWR for channel 1 reads higher than the SWR on channel 40, the antenna/antennas are electrically “Short”. The CB antenna should be lengthened by adjusting the antenna or adding springs or quick disconnects etc. Adjustments should be made in 1/8″ increments when possible. You should also mark the antenna/antennas original position and the position of each adjustment along the way.
If the SWR for channel 40 reads higher than the SWR on channel 1, the antenna/antennas are electrically “Long”. The CB antenna should be shortened by adjusting the antenna/antennas. Some will actually need to be cut or modified to make them shorter. Adjustments should be made in 1/8″ increments when possible. You should also mark the antenna/antennas original position and the position of each adjustment along the way.
If after making the above corrections the SWR on all channels is about 2.0 but not in the “Red Zone”, the antenna cable may be of poor quality, the wrong length, etc.. The ground plane may be insufficient or you may have an ungrounded antenna mount.