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RF Calculator

Wavelength, SWR and power

RF relationships, shown together

Frequency sets wavelength and component reactance. Forward and reflected power set reflection coefficient, SWR, return loss and mismatch loss. These describe the measured point in a feed system; they do not prove antenna efficiency.

Wavelength 21.112 m
Half-wave 10.556 m · Quarter-wave 5.278 m
SWR 1.50:1 · Reflection coefficient 0.200
Return loss 13.98 dB · Mismatch loss 0.177 dB
40.0 dBm = 10.000 W
XL 892.2 Ω · XC 112.1 Ω
LC resonance 5.0329 MHz
Wavelength at 14.200 MHzλ = 21.112 mFeed-line power at measurement pointTX / meterLoadForward 100.0 WReflected 4.0 W · SWR 1.50:1Component reactance at 14.200 MHzL 10.000 µH · XL 892.2 ΩC 100.00 pF · XC 112.1 ΩLC resonance 5.0329 MHz
Diagram follows entered frequency, power and component values. Arrows show power direction at the measurement point, not antenna efficiency.

Wavelength

λ = c ÷ f using 299,792,458 m/s. Feed-line velocity factor is separate.

SWR

ρ = √(Pr ÷ Pf), then SWR = (1 + ρ) ÷ (1 − ρ). Reflected power must remain below forward power.

Reactance

XL = 2πfL and XC = 1 ÷ 2πfC. Ideal LC resonance occurs where their magnitudes are equal.