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Wilkinson divider calculator

What it has over a plain T-junction

The balancing resistors. In a Wilkinson the outputs are isolated from one another: a reflection from one antenna does not crawl into its neighbour but is dissipated in the resistor. Cables simply soldered in parallel give no such isolation and spoil the match of the whole system.

input 50 Ω√N·Z₀√N·Z₀R = 2·Z₀output Z₀output Z₀λg/4in balanced operation no current flows through the resistor
Branches of √N·Z₀, λ/4 long, with a balancing resistor of 2·Z₀ between the outputs
Frequency (MHz)
Number of output ports (N)
Port impedance (Ω)
Branch cable
Insulation material
ε of the insulation
Result: line sections
Branch impedance (√N · Z₀)
Branch length (λg/4)
Balancing resistor
The same between a pair of outputs
Power split
Result: LC equivalent
Branch inductance
Capacitance at the input
Capacitance at each output

📐 The formulas​

Branches made from line sections:

Z_br = √N × Z₀
L    = λg/4 = 299792.458 / (f × √ε) / 4    [mm]
R    = Z₀   from each output to the common node

The resistors are connected in a star: each output goes through Z₀ to a common node. Between two adjacent outputs that gives 2 × Z₀ — for the classic two-way divider, the familiar 100 Ω.

Power split:

Loss per port = 10 × lg(N)   [dB]

The LC equivalent (for frequencies below about 100 MHz, where the sections get too long):

L    = 10³ × Z_br / (2π × f)      [nH]
C    = 10⁶ / (2π × f × Z_br)      [pF]  at each output
C_in = N × C                       [pF]  at the input

Symbols:​

  • N — the number of output ports
  • Z₀ — the port impedance (usually 50 Ω)
  • ε — the permittivity of the branch dielectric
Where this calculator stops:
  • The calculation assumes an equal power split between all the ports
  • The isolation is at its best only at the design frequency
  • The resistors must be non-inductive; at power, work out the dissipation
  • The LC version has a narrower bandwidth than the line version and is sensitive to component tolerance

🎯 In practice​

  • Feeding antenna arrays: two or four identical antennas from one radio.
  • Combining the power of two amplifiers in phase.
  • Splitting a receive path between several receivers without them interacting.
Practical advice:
  1. For N = 2 you need 70.7 Ω — people use 75 Ω cable, and the SWR barely suffers. There is then a single resistor: 100 Ω between the outputs.
  2. The branch lengths must match to the millimetre: a difference skews the phase and unbalances the split.
  3. In balanced operation the resistors stay cold. If they get warm, the antennas are unbalanced — find out why.

© 2026 UR3PKI · CyberDev.Space · Content licensed under CC BY-NC-SA 4.0.

How to cite this calculator
UR3PKI. «Wilkinson divider calculator». CyberDev.Space. https://cyberdev.space/en/radio/calculators/others/wilkinson (licence CC BY-NC-SA 4.0).

The licence lets you use this material freely, including in teaching materials, but only with attribution to the author and a link to the source.

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