This parallel wire impedance calculator finds the characteristic impedance of a two-wire transmission line from the conductor spacing and diameter. Enter the values above.
Formula
Z₀ = (276 ÷ √εr) × log₁₀(2D ÷ d)
- D — center-to-center spacing, d — wire diameter
Example
D = 10 mm, d = 1 mm, air: Z₀ = 276 × log₁₀(20) = 359 Ω.
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Frequently Asked Questions
How do I calculate two-wire line impedance?
Use Z0 = (276 / sqrt(er)) x log10(2D/d), with the spacing and wire diameter.
What is 300-ohm twin-lead?
A two-wire line spaced to give about 300 ohms, once common for TV antenna feeds.
Does wider spacing raise impedance?
Yes. More spacing between the wires increases the characteristic impedance.