This tool computes the Return loss (in dB) from Voltage Standing Wave Ratio (VSWR).
Γ = (VSWR – 1)/(VSWR + 1)
Return Loss (dB) = -20*Log10(|Γ|)
A good value of VSWR is 1.5, where 96% of the power is transmitted forward and only 4% is reflected back (mismatch loss calculator) In this case, the return loss is calculated to be 14 dB.
A higher numerical value of VSWR represents a poor match. Conversely a lower VSWR value represents a good match.
As well, a higher value of VSWR converts to a lower dB value of return loss. For instance a VSWR of 2.5 translates to a return loss of 7.4 dB.
The ideal value of VSWR is 1 where none of the power is reflected back. It represents an excellent match. Note that the minimum value of VSWR is 1 – i.e. VSWR cannot be less than 1. There is no maximum value of VSWR and so it is designated as infinity ∞ .