VSWR & Return Loss Calculator

Yes, but most modern radios include protection. When reflected power returns to the PA output, it adds to the transistor's output voltage stress and can cause thermal runaway, gate oxide breakdown (in FETs), or second-breakdown (in bipolars). At modest VSWR (2:1 to 3:1), the risk is primarily long-term degradation from repeated thermal stress rather than immediate failure. At severe mismatch (VSWR >5:1 or an open/short circuit), the reflected voltage can spike to twice the incident voltage and immediately damage unprotected amplifier stages. Modern solid-state transceivers protect against this by monitoring reflected power and reducing drive before the reflected power reaches dangerous levels. Older tube-type transmitters are more tolerant of high VSWR because tubes can absorb transient voltage spikes more readily than solid-state devices, which is one reason experienced operators with legacy equipment sometimes accept higher VSWR than would be acceptable in a modern solid-state rig.

For most commercial WiFi applications, a VSWR of 2:1 or better (return loss ≥ 9.5 dB) is entirely adequate. At 2:1 VSWR, only 11% of the transmit power is reflected, representing a 0.51 dB mismatch loss - well within the noise of other factors like channel conditions, interference, and multipath. WiFi access point hardware is designed to work reliably with replacement antennas from various vendors, and a VSWR of 2:1 allows interchangeability without performance concerns. For the receive path, a higher VSWR does slightly reduce the effective gain of the receive antenna, but this is rarely the limiting factor in WiFi link performance. Only in very high-performance point-to-point WiFi bridge installations (where every tenth of a dB matters for maximum range) is VSWR tightened below 1.5:1.