VSWR to Return Loss Calculator
Evaluate impedance matching quality. Instantly convert VSWR to Return Loss, Reflection Coefficient, and Mismatch Loss. Free online tool for RF engineers.
Derived Metrics
Standing Wave Visualization
VSWR Quick Reference
Engineering Principles: Impedance Mismatch & Reflection
Voltage Standing Wave Ratio (VSWR) measures how efficiently radio-frequency power is transmitted from a source, through a transmission line, into a load. A perfect match means no power is reflected.
Ratio of reflected voltage wave amplitude to incident wave.
The loss of signal power returned/reflected by a discontinuity.
Power lost from the transmitted signal due to reflection.
Technical Notes
- •A VSWR of 1.0:1 is ideal (100% power transfer).
- •VSWR generally increases with frequency due to parasitic effects.
- •Return Loss is always a positive number in dB (representing loss), though mathematically the coefficient calculation yields a negative gain.
Frequently Asked Questions
What is a good VSWR reading?
For most commercial applications, a VSWR of 1.5:1 or less is considered excellent (less than 4% reflected power). In critical systems, 1.2:1 may be required. Values above 2.0:1 generally indicate a problem that needs to be addressed.
What causes high VSWR?
High VSWR is caused by an impedance mismatch between the source/cable and the load (antenna). Common causes include damaged cables, loose connectors, incorrect cable impedance (using 75Ω instead of 50Ω), or antennas operating outside their designed frequency band.
How does Return Loss relate to VSWR?
Return Loss and VSWR measure the same phenomenon but in different units. Return Loss (dB) is often preferred by engineers because it provides better resolution for tuning well-matched systems. For example, improving VSWR from 1.1 to 1.05 looks small, but in Return Loss it's a significant jump from 26dB to 32dB.