What is standing wave ratio?

Standing wave ratio, also known as VSWR and SWR, is short for Voltage Standing Wave Ratio in English. It refers to the ratio of standing wave belly voltage to trough voltage amplitude, also known as standing wave coefficient and standing wave ratio. It is used to indicate whether the antenna and the radio transmitter match.

If the value of SWR is equal to 1, it means that the radio waves transmitted to the antenna have no reflection and are all transmitted, which is the most ideal situation. If the SWR value is greater than 1, it means that some of the electric waves are reflected back and eventually become heat, which causes the feeder to heat up. The reflected electric wave can also generate a relatively high voltage at the output of the launch pad, possibly damaging the launch pad.