RF · antenna match
VSWR and return loss calculator.
Enter VSWR or return loss and read the reflection coefficient, mismatch loss and power delivered.
Inputs
Match
Enter values to calculate.
How do I convert VSWR to return loss?
Start from the reflection coefficient: Gamma = (VSWR - 1) / (VSWR + 1). Then return loss = -20 log10 |Gamma| dB, VSWR = (1 + |Gamma|) / (1 - |Gamma|), and mismatch loss = -10 log10 (1 - |Gamma|2) dB. The fraction of power reflected is |Gamma|2.
Worked example. A VSWR of 2:1 gives a reflection coefficient of 0.333, a return loss of 9.54 dB, a mismatch loss of 0.51 dB, and about 11.1 percent of the power reflected.
A perfect match is VSWR 1 and infinite return loss. The numbers describe the mismatch at the point you measured; cable loss between the meter and the antenna can make the antenna look better matched than it is.
Frequently asked questions
What VSWR is 20 dB return loss?
About 1.22:1.
What is mismatch loss?
The power lost to reflection, as 10 log10 of the delivered fraction. It is 0.51 dB at VSWR 2:1.
Is VSWR the same as SWR?
In antenna work the terms are used interchangeably; VSWR is the voltage standing wave ratio.
Can VSWR be less than 1?
No. It is 1 or more, with 1 a perfect match.
Sources
Checked
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Scope
Arithmetic only. Measure real VSWR with a calibrated analyser.