This calculator allows you to determine the voltage standing wave ratio (VSWR) from the forward and reflected powers measured in an RF system. It helps evaluate the quality of impedance matching between a transmitter and a load.
It is useful for RF engineers, maintenance technicians and radio amateurs who need to verify the performance and efficiency of their transmission lines and antennas.
Formula
VSWR = (1 + √(Pr / Pf)) / (1 – √(Pr / Pf))
Explanation of the formula
- P f represents the direct power transmitted to the load.
- P r is the reflected power due to impedance mismatch.
- The Pr/Pf ratio indicates the proportion of energy returned to the source.
- A VSWR close to 1:1 means perfect matching, while a high value indicates significant power loss.
Calculation of VSWR for 100 W of direct power and 5 W of reflected power
Input : P f = 100 W, P r = 5 W
Output : VSWR ≈ 1.73:1
Benefits and uses
- Quickly checks the impedance matching of an RF system.
- Avoids power losses due to wave reflections.
- Essential for maintaining RF antennas and amplifiers.
- Used to diagnose mismatch problems in transmission networks.