VSWR / Return Loss / Γ
Enter any one of VSWR, return loss, or reflection coefficient — get all of them plus mismatch loss.
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The engineering
Three languages for the same mismatch. VSWR 2:1 is return loss 9.5 dB is |Γ| 0.33 — 11% of your power bouncing back and only 0.51 dB of mismatch loss, which is why a 2:1 antenna still radiates fine but your transmitter's PA may still complain.
Mismatch loss is what you actually lose; return loss is what the analyzer shows. Don't budget with the wrong one.
Where this math comes from
Standing waves on lines are Heaviside-era physics, but making mismatch visible was the slotted line's job — sliding a probe along a line and reading the ratio of maxima to minima, the literal 'voltage standing wave ratio.' Phillip Smith's 1939 chart turned the arithmetic of Γ into geometry an engineer could do with a pencil.
The vector network analyzer (HP 8410, 1967) retired the slotted line and made return loss the everyday number; the trio on this card is the same quantity wearing three uniforms.
- 1885Oliver HeavisideTransmission-line theory — reflections quantified.
- 1939Phillip H. SmithThe Smith chart — reflection made graphical.
- 1967Hewlett-Packard8410 network analyzer moves matching from slotted lines to screens.
See the full timeline of the math behind every calculator →
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