Calculate wavelength, β, reflection coefficient, standing-wave voltage/current, reflected power, input impedance and local coax loss.
Use this calculator at your own risk. The results are theoretical/engineering estimates and must not be used as the sole basis for operating a transmitter, transmission line, antenna system, or RF installation.
RF systems can produce dangerous voltages, currents, temperatures and electromagnetic fields. High-power RF can cause burns, fire, equipment damage, arcing and other hazards. An apparently acceptable calculated result does not guarantee safe operation.
Cable power ratings depend on installation, ambient temperature, ventilation, cable condition, connectors, frequency, VSWR, duty cycle and other factors. Always check the manufacturer's specifications and applicable safety regulations, and use appropriate protection and measurement equipment.
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Enter the load impedance as ZL = RL + jXL. Positive X is inductive; negative X is capacitive.
Results are currentThe diagram is a simplified Smith-chart-style display of the complex reflection coefficient.
Red point: load impedance ZL at the load end.
Blue point: input impedance Zin seen by the transmitter.
The two points therefore show how the termination is transformed by the transmission line.
For a lossy line, the magnitude of the reflection coefficient becomes smaller towards the transmitter because the reflected wave is attenuated on its return path.
Center: matched load, Γ = 0.
Right: open circuit, Γ = +1.
Left: short circuit, Γ = −1.
λo = c/f
λ = VF*λo
β = 2π/λ
ΓL = (ZL − Zo)/(ZL + Zo)
Γin = ΓLe−2(α+jβ)L
Zin = Zo(1 + Γin)/(1 − Γin)
SWR = (1 + |Γ|)/(1 − |Γ|)
α = loss*ln(10)/(20*100), where α is the amplitude attenuation constant in Np/m.
P+(x)=P+(0)e−2αx
For a lossy line, the reflected wave at position x is calculated from the reflected wave at the load, including its attenuation on the return path.
ploss(x)=R'|I(x)|2, with R' approx 2αZo for a low-loss line.
This is an engineering estimate. Actual cable loss, velocity factor, thermal rating, installation and connector losses should be taken from the cable manufacturer's data.