VSWR Calculator
Convert between VSWR, return loss, and reflection coefficient.
VSWR Reference Table
| VSWR | Return Loss | Reflected | Quality |
|---|---|---|---|
| 1.0:1 | ∞ dB | 0% | Perfect |
| 1.2:1 | 20.8 dB | 0.8% | Excellent |
| 1.5:1 | 14.0 dB | 4% | Good |
| 2.0:1 | 9.5 dB | 11% | Acceptable |
| 3.0:1 | 6.0 dB | 25% | Poor |
| 5.0:1 | 3.5 dB | 44% | Bad |
| 10.0:1 | 1.7 dB | 67% | Very Bad |
Understanding VSWR
What is VSWR?
Voltage Standing Wave Ratio (VSWR) measures impedance mismatch between a transmission line and its load (antenna). A perfect match is 1:1. Any mismatch causes some power to reflect back toward the transmitter.
Key Formulas
VSWR = (1 + |Γ|) / (1 - |Γ|)
|Γ| = 10^(-RL/20)
Reflected Power = |Γ|² × 100%
|Γ| = 10^(-RL/20)
Reflected Power = |Γ|² × 100%
Acceptable VSWR Levels
- ≤ 1.5:1: Excellent for most applications
- ≤ 2.0:1: Acceptable for HF/VHF mobile
- ≤ 3.0:1: Maximum for many solid-state radios
- > 3.0:1: Risk of transmitter damage
Why VSWR Matters
- High VSWR wastes transmitter power
- Reflected power can damage transmitters
- Standing waves cause hot spots in cables
- Indicates antenna tuning issues