Signal Wavelength in Cable

Enter frequency + velocity factor to compute wavelength in cable, plus quarter-wave and half-wave lengths.

How to Use

  1. Enter a frequency and select units (Hz, kHz, MHz, GHz).
  2. Enter velocity factor (VF) for your cable (example: 0.66, 0.78, 0.85).
  3. Choose output length units (m, cm, ft, in).
  4. Open “Show Work” to see the formulas and steps.
Cable Wavelength
λ = (c × VF) / f
λ (cable)
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¼λ
—
½λ
—
λ (free)
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Status: —
λ (cable)
½λ
¼λ

Visualization is proportional (¼λ and ½λ are shown relative to λ). For exact numbers, see outputs.

Inputs & Settings
Results update instantly. Share link is generated only by button.
Examples: 27 MHz (CB), 146 MHz (VHF), 915 MHz (ISM), 2.4 GHz (Wi-Fi)
VF is usually 0.6–0.9 for coax. Use your cable datasheet when possible.
Auto rounding adapts based on the size of the result.
λ₀ uses speed of light in free space; cable wavelength uses VF.
Show Work (step-by-step)
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Work is shown in base units: Hz and meters, using c = 299,792,458 m/s.

Reference

Cable wavelength: λ = (c × VF) / f

  • Quarter-wave: ¼λ = λ / 4
  • Half-wave: ½λ = λ / 2
  • Free-space: λ₀ = c / f
Where c = 299,792,458 m/s, VF is unitless (0–1 typical), f is frequency in Hz, λ is in meters.

FAQ

What is velocity factor?

Velocity factor (VF) is how fast a signal travels in a cable compared to the speed of light. A VF of 0.66 means the signal travels at 66% of c.

Why does wavelength change in a cable?

Because propagation speed is lower in the dielectric. Frequency stays the same, so lower speed means shorter wavelength.

Should I cut exactly ¼λ?

Often you leave trimming margin and verify, because connectors, bends, and nearby objects can shift the effective electrical length.

Does this apply to transmission line matching?

Yes—electrical lengths (¼λ, ½λ, etc.) are foundational for stubs, phasing lines, and impedance transforms. Use the cable’s VF for best results.

Tool Info

Last updated:

Updates may include UI improvements, unit support, and calculation edge-case handling.