VSWR vs Return Loss Cheat Sheet

When an electric wave travels through an antenna system—including the receiver, feed line, antenna, and free space—it encounters impedance variations at different interfaces. These variations cause part of the wave’s energy to reflect back toward the source, creating a standing wave within the feed line. The degree of this reflection is quantified using the voltage standing wave ratio (VSWR), which measures the ratio of maximum to minimum power in the wave.

A lower VSWR indicates better power transfer, reducing energy loss. Ideally, a VSWR of less than 1.5:1 ensures efficient signal transmission. In low-power applications where power loss is critical, a VSWR of up to 2:1 is marginally acceptable. However, with appropriate equipment, systems may still function with a VSWR as high as 6:1.

For those who prefer a simplified approach over mathematical equations, a reference table can be used to correlate VSWR values with the percentage of power reflected back to the source. Lower VSWR values correspond to minimal reflected power, maximizing the efficiency of the antenna system.