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VSWR Mismatch Calculator is a handy utility designed to process VSWR data. VSWR is a common specification in data sheets for RF devices, such as amplifiers, sources, and power meters.

At small VSWRs, the plus and minus converge to the same value. At higher VSWRs, the plus and minus uncertainties diverge, so you need to calculate both. As an example, consider a Agilent ESG-3000 microwave source operating at 900 MHz. Its VSWR is specified at 1.4 to 1. Then, assume that you measure the source's output power with a Agilent E4412A power sensor that has a specified VSWR of 1.15 to 1. If you input these figures into the VSWR Calc program, you obtain the screen shown in the screen shot above.

The "Copy to Clipboard" function transfers the VSWRs and the calculated data to the Windows clipboard so that documenting the calculations is easy in any Windows application. (The cardboard slide rule cannot perform this function.). The uncertainty in the example is +0.100 to –0.102 dB. You should know the measurement uncertainty, because it is relatively easy to obtain totally uncertain measurements at high frequencies if the VSWRs are uncontrolled or unknown.