SWR calculator and RF tools
How much power reaches the antenna at an SWR of 2? How much does the cable attenuate? The RF calculators answer everyday questions at the radio desk with worked steps so the result stays traceable.
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What the page does
- SWR, reflection coefficient, return loss, mismatch loss
- Convert dBm, dBW, watts and volts
- Cable loss by type and length
- Resonant circuit, wavelength, filters
- Formula collection with all equations
Background
Standing wave ratio follows from the magnitude of the reflection coefficient: SWR = (1 + |Γ|) / (1 − |Γ|). At an SWR of 2, |Γ| = 1/3; about 11 % of the power is reflected, roughly 0.5 dB. An SWR of 1.5 or 2 is usually uncritical in operation – what matters is what the final stage tolerates and how much extra loss the cable adds.
In practice
How it works: enter the measured SWR or the load impedance; the calculator gives reflection coefficient, return loss and the share of reflected power. Add cable type and length for the line loss. A long, lossy cable makes the SWR at the radio look better than it is at the antenna – the calculator shows that too.
Frequently asked questions
Above which SWR should I stop transmitting?
It depends on the radio; many transceivers reduce power above about 2 to 3. The manual is authoritative.
Does a tuner lower the SWR at the antenna?
No. It matches the load for the radio; the mismatch on the cable to the antenna remains.