Answer 5—The SWR should be kept to 1.05 or less. The health of any transmitter is decided by how well its output impedance is matched to its load (antenna). The standing wave ratio (VSWR or ISWR) is a measure of how well it is matched. A value greater than one indicates improper matching of the output circuit with the transmission line and load.

A high SWR means that peak voltages and currents in the transmitter output stage and in the transmission line itself are higher than they need to be, causing extra stress and reducing component lifetimes. This also reduces the design margin for external stresses such as lightning, etc.

Contributor: M.K. Suvarnakumar

Published January 2004