What is an acceptable VSWR?
Whilst there are lots of Rules of Thumb (ROT) proposed, the answer lies in determining the loss and power handling of the transmission line in the intended scenario, and making a decision about whether they are acceptable. In general, • coaxial transmission lines (by virtue of the lower Zo and small conductor sizes) are relatively higher loss, and high VSWR and length together result in higher loss overall; and • open wire transmission lines (by virtue of the higher Zo and larger conductor sizes) are relatively lower loss and high VSWR and length increases loss, but often lower loss than coaxial lines for the same scenario. To model the effect of VSWR on transmission line, try the RF Transmission Line Loss Calculator . Equipment specifications is another potential source of guidance on acceptable VSWR from a load point of view.