VSWR vs Return Loss Parallel Table VSWR (Voltage Standing Wave Ratio) is a measure of how efficiently radio-frequency power is transmitted from a power source, through a transmission line, into a load (for example, from a power amplifier through a transmission line, to an antenna). Return loss is a logarithmic ratio of the power reflected from a system to the power entering that system, as defined in Equation 1. Return loss is expressed in decibels. The higher the number, the lower the amount of reflected energy.