SWR is an acronym for “Standing Wave Ratio”.  It is a measure of how well the antenna is tuned to the CB band.  Any problems with the antenna, antenna cable, or antenna mount will show up during an SWR check.

Please note that the SWR is a measure of antenna performance.  A poor SWR is caused by the antenna, the antenna cable, or a poor antenna installation.  Poor SWR is not caused by the radio. 

The SWR should be below 3.  If the SWR gets higher than 3, then you will experience short range and the transmitter in the radio may overheat and eventually fail.  It is not mandatory to check the SWR, but if you are experiencing performance issues (short range) then it should be checked to ensure that the antenna is functioning properly.