Antenna tuning is the process of adjusting the Standing Wave Radio (SWR). If the SWR is too high, then you may run the risk of damaging your equipment if the antenna is not properly tuned to the recommended limits.[1]
How will a high SWR damage my equipment? Damage to a radio can occur if there is too much power being reflected back into the radio. High SWR readings can be reduced by either lengthening or shortening the antenna.[2]
Not all Citizen Band (CB) radios come with a built-in SWR meter, and in order to tune your antenna you’ll need an external meter, like the one below, to get your rig up and running.[3] In addition to protecting your radio with a properly tuned antenna, transmit and receive performance will be improved.
The President McKinley radio is an example of a CB radio with a built-in SWR meter.[1]
If you are using an external meter, below are the steps for tuning a CB antenna. If your radio has a built-in meter, then you can begin on #5 below after connecting the coax cable to the back of the radio. SWR readings of 2 or lower on channels 1, 20, and 40 are preferable.
1) Turn Off CB radio.
2) Disconnect the antenna coax cable from back of the radio.
3) On the back of the meter, connect one end of your antenna coax cable to the SWR meter where it indicates ‘ANT’.
4) Connect a short coax cable (may not be supplied) to the back of the meter where it indicates either ‘RADIO’ or ‘TRANS’. Connect the other end of the cable to the antenna connection on the rear of your CB radio.
5) Turn on the CB and select Channel 1 on the radio.
6) Switch the meter to the ‘FWD’ (forward) position.
7) Close the doors, hood (and trunk if applicable) of the vehicle.
8) Key the microphone and turn the knob on the SWR meter until the needle indicates the set position.
9) Release the microphone and switch the meter to ‘REF’ (reflect) position.
1 0) Key the microphone. The red needle on the SWR meter will indicate the reading. Make note of the reading to be used for antenna adjustment purposes.
11) Turn the CB radio to channel 40 and repeat steps 7 through 10.
12) The next step is adjusting the antenna for maximum performance. The lower the SWR reading on the meter, the better performance you’ll receive out of your radio. The goal is to set the antenna to the lowest SWR possible evenly across the 40-channel bandwidth.
Example: On Channel 1, the SWR reading is 1.5, and on Channel 40 the reading is 1.5. By adjusting the antenna evenly over the 40-channel bandwidth, your radio will perform well on any channel selected.
If the SWR reading was higher on Channel 40 than on Channel 1, the electrical length on your antenna is too long. You will need to trim down or adjust down the electrical length of the antenna.
If the SWR reading was higher on channel I than on channel 40, the electrical length on your antenna is too short. If you have a tunable tip or steel rod type antenna raise or adjust the length of the antenna to the highest point. Re-check the SWR on Channel 1 and 40 with the meter. If a lower reading cannot be attained, then you can add a spring, lengthen the coax cable or re-position the antenna.
It is important that you don’t operate the radio until a SWR reading of less than 3 is achieved.
If you have an antenna with a tunable tip (e.g. Firestik), then you can use the steps below to adjust the SWR.[1]
Tunable Tip: Remove cap. To adjust the antenna, turn the screw to a lower or higher position. Replace cap and re-check SWR on Channels 1 and 40. Repeat this step until low SWR is achieved on Channels 1 and 40.
Fiberglass: Remove cap. If SWR is higher on Channel 40 than it is on channel 1, pull small amount of wire out from the end of the antenna and cut it off. Press the wire back down against the coiled wire inside of the jacket.
Note: The wire should not be sticking straight up. Replace cap re-check the SWR on Channels 1 and 40. Repeat this step until a low SWR is achieved on Channels 1 and 40.
Steel Rod: Loosen the setscrew. Press the rod to the bottom, and then raise it slightly. Re-tighten the setscrew. Re-check the SWR on Channels 1 and 40. If the SWR reading is higher on Channel 40 than on Channel 1, remove the rod and cut a small amount from the bottom of the rod off. Repeat this step until a low SWR is achieved on Channels 1 and 40.
[1] Firestik Antennas – https://www.rightchannelradios.com/collections/firestik-cb-antennas
[1] Right Channel Radios, President McKinley – https://www.rightchannelradios.com/products/president-mckinley-ssb-radio
[1] Right Channel Radios, Understanding SWR – https://www.rightchannelradios.com/blogs/installation-guides/18428275-understanding-swr
[2] Troubleshooting High SWR Readings – https://www.wearecb.com/troubleshoot-a-high-swr.html
[3] Right Channel Radios – https://www.rightchannelradios.com/