SWR, or standing wave ratio, is an electrical measurement that assesses a CB radio system's resonance with the 11-meter, Citizen's Band frequencies. When the radio and antenna achieve matching impedance levels, the SWR measurements will fall below a 2:1 ratio, and the CB radio will efficiently transmit at a maximum power and distance. Tune your Firestik CB antenna with an SWR meter and maximise your radio's potential.
Check the antenna installation for continuity using a multimeter. Park your car in an open area, and be sure all doors are closed before measuring the SWR.
Connect the CB radio to the SWR meter's transmitter terminal using the patch cable. Connect the antenna cable to the antenna terminal of the SWR meter.
Set the radio to channel 1, and to AM mode, if the radio is equipped with side band functionality. Set the SWR switch to "Forward."
Press and hold the transmit button on the radio's handset. Adjust the meter's "Set" knob until the needle lines up with the set marker on the meter face. Flip the SWR switch to "Reference" or "SWR." Record the value of the meter's position to one decimal place, and release the transmitter button.
Set the radio to channel 19, set the switch to "Forward" and align the needle to the set position. Flip the switch to "Reference," record the needle's value and release the transmitter.
Set the radio to channel 40, and perform the procedure to find the SWR value for this channel.
Adjust electrical continuity of your antenna, according to the three SWR readings. If all three readings fall between 2.0 and 3.0, then an electrical grounding problem may exist. If all three readings fall above 3.0, then an electrical short or an antenna mount problem may be the case.
Adjust the length of your antenna according to the readings. If the reading of channel 1 is higher than channel 40, the antenna must be lengthened by adjusting the mount or turning the tip screw. If the reading of channel 40 is higher than channel 1, the antenna must be shortened by adjusting the tip screw, by removing insulation and clipping a portion of the antenna tip or by lowering the metal whip.
If you have a wire-wound antenna, attach the rubber tip to the top of the antenna during SWR testing. Apply soap and water to the rubber tip for quick removal when adjusting the antenna.
Tips and warnings
- If you have a wire-wound antenna, attach the rubber tip to the top of the antenna during SWR testing. Apply soap and water to the rubber tip for quick removal when adjusting the antenna.
Things you need
- SWR meter
- Coaxial patch cable, 50-ohm, PL-259 connectors on both ends
- Wire clippers
- Utility knife