This tool computes the mismatch loss from Voltage Standing Wave Ratio (VSWR).
Γ = (VSWR – 1)/(VSWR + 1)
Return Loss (dB) = -20*Log10(|Γ|)
Mismatch Loss (dB) = -10*Log10(1 – |Γ|2)
Reflected Power (%) = 100*(|Γ|2)
Transmitted Power (%) = 100*(1 – |Γ|2)
For a VSWR of 2, the mismatch loss is calculated to be 0.51. 89% of the power is transmitted forward, while 11% is reflected back into the source. As the VSWR increases, the quality of the match deteriorates and more power is reflected back. For a VSWR of around 5.9, half the power is reflected back.
A good value of VSWR is 1.5, where 96% of the power is transmitted forward and only 4% is reflected back. The ideal value of VSWR is 1 where none of the power is reflected back.