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Tool 11 · Available

Coax Cable Calculator

Turn supplied cable or datasheet values into loss, delivered power, delay, and phase length.

Typical inputs
Frequency, length, nominal Z0, velocity factor, user-supplied attenuation, input power, and attenuation tolerance.
Calculated output
Total loss, delivered power, delay, guided wavelength, electrical length, and tolerance range.
Model status
Release C · documented and numerically tested
Engineering question

What do this cable’s stated attenuation and velocity factor do over the installed length?

Datasheet-value coax model

Supply matched attenuation at the operating frequency from the actual datasheet or measurement. No named-cable database or silent interpolation is implied.

Output power17.5000 dBm2.5000 dB matched cable loss; connectors and mismatch excluded
Output power
56.2341 mW
Nominal impedance
50.0000 Ω
context only; this matched delay/loss model is invariant to Z₀
One-way delay
50.54 ns
Guided wavelength
80.7604 mm
Cable wavelengths
123.82304 λg
Electrical length
44576.293°
Length-tolerance phase
±445.763°
Frequency-tolerance phase
±0.000°
constant VF approximation

Calculation path

  1. Loss=0.25 dB/m×10 m=2.5000 dB\text{Loss}=0.25\,\mathrm{dB/m}\times10\,\mathrm m=2.5000\,\mathrm{dB}
  2. τ=ℓVF⋅c\tau = \frac{\ell }{\mathrm{VF}\cdot c}
  3. λg=VF cfθ=360∘ℓλg\lambda_g=\frac{\mathrm{VF}\,c}{f}\qquad\theta=\frac{360^\circ\ell}{\lambda_g}
  4. Braid construction, roughness, connectors, bends, mismatch, temperature, aging, and installation damage are not modeled.
Model

What this calculator is doing

The calculator uses supplied cable values instead of an unversioned cable-name database. Nominal Z0 is context; this simple matched delay/loss calculation is invariant to it.

Decision

How to read the result

Use attenuation at operating frequency and add connectors or mismatch separately. Precision work needs manufacturer data across frequency and temperature.

Equations & conventions

  • Loss=αdatasheet ℓ\text{Loss}=\alpha_{\mathrm{datasheet}}\,\ell
  • τ=ℓVF⋅c\tau = \frac{\ell }{\mathrm{VF}\cdot c}
  • λg=VF cf\lambda_g=\frac{\mathrm{VF}\,c}{f}
  • Attenuation is a positive one-way magnitude in dB per metre.
  • VF sets phase velocity; Z0 is nominal real characteristic impedance.
  • Tolerance is applied to supplied attenuation.

Independently checked example

Checked default: 10 m at 0.25 dB/m gives 2.5 dB loss, so 20 dBm becomes 17.5 dBm; VF 0.66 gives about 50.54 ns one-way delay.

Common mistakes

  • Using catalogue loss from the wrong frequency.
  • Double-counting loss embedded in an end-to-end measurement.

Assumptions, validity & omissions

  • Attenuation is user-supplied at the operating frequency.
  • No unsourced cable-name library is implied.
  • Connectors and mismatch require separate entries.

Sources & model provenance

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