Coaxial Cable Loss

α = 8.686 × R / (2 × Z0) dB/m

Quick answer

This calculator solves α ≈ 8.686 × R_conductor / (2 × Z₀) [dB/m, approximate] for Loss per Meter. With Resistance per Meter 1.1, Characteristic Impedance 0.47 kΩ, the result is 0.01016. It solves in 3 directions, so you can enter the values you have and get the one you need.

Calculator

Loss per Meter
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Formula

α ≈ 8.686 × R_conductor / (2 × Z₀) [dB/m, approximate]

Description

Coaxial cable attenuation is dominated by conductor losses at lower frequencies and dielectric losses at higher frequencies. The conductor loss component is approximately 8.686 × R/(2Z₀) dB/m, where 8.686 = 20/ln 10 converts the nepers-per-metre result to decibels, and R is the total resistance per unit length of the inner and outer conductors (including skin effect). At higher frequencies, the dielectric loss term (proportional to frequency and dielectric loss tangent) becomes significant. Total cable loss increases with frequency (roughly as √f for conductor loss) and is the primary factor limiting cable run lengths in RF and broadband systems.

Variables

  • α — Attenuation coefficient (dB/m, approximate)
  • R — Conductor resistance per meter (Ω/m, including skin effect)
  • Z₀ — Cable characteristic impedance (Ω)

Practical Notes

This formula gives only the conductor loss component. For a complete model, add dielectric loss: α_total = α_conductor + α_dielectric. Typical losses at 1 GHz: RG-58 ≈ 0.7 dB/m, RG-213 ≈ 0.27 dB/m, LMR-400 ≈ 0.11 dB/m. Lower impedance cables (Z₀ = 50 Ω) have slightly higher loss than higher impedance cables (Z₀ = 75 Ω) of the same size because more current flows for the same power. Always use manufacturer-specified loss curves for accurate link budget calculations.

Symbols and units

Symbol Meaning Default unit Accepted units
alpha Loss per Meter — —
R Resistance per Meter — —
Z0 Characteristic Impedance Ω mΩ, Ω, kΩ, MΩ

Step by step

  1. 1. What you know: Resistance per Meter 1.1, Characteristic Impedance 0.47 kΩ
  2. 2. The relation: α ≈ 8.686 × R_conductor / (2 × Z₀) [dB/m, approximate]
  3. 3. Substitute: R = 1.1, Z0 = 0.47 kΩ
  4. 4. Result: Loss per Meter = 0.01016

Worked examples

Minimum range

Given: Resistance per Meter 0.055, Characteristic Impedance 1 Ω

Result: Loss per Meter = 0.2389

Low range

Given: Resistance per Meter 0.55, Characteristic Impedance 10 Ω

Result: Loss per Meter = 0.2389

Typical

Given: Resistance per Meter 1.1, Characteristic Impedance 0.47 kΩ

Result: Loss per Meter = 0.01016

High range

Given: Resistance per Meter 1.76, Characteristic Impedance 4.7 kΩ

Result: Loss per Meter = 0.001626

Maximum range

Given: Resistance per Meter 17.6, Characteristic Impedance 47 kΩ

Result: Loss per Meter = 0.001626

Solving for each variable

Solve for Loss per Meter

Resistance per Meter 0.055, Characteristic Impedance 1 Ω → 0.2389

Solve for Resistance per Meter

Loss per Meter 0.025, Characteristic Impedance 1 Ω → 0.005756

Solve for Characteristic Impedance

Loss per Meter 0.025, Resistance per Meter 0.055 → 9.555 Ω

How Loss per Meter changes with Resistance per Meter

Resistance per Meter (input) Loss per Meter (result)
0.11 0.001016
0.275 0.002541
0.55 0.005082
0.825 0.007623
1.1 0.01016
1.65 0.01525
2.2 0.02033
4.4 0.04066
7.7 0.07115
11 0.1016

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Frequently asked questions

How do you calculate Coaxial Cable Loss?

Use α ≈ 8.686 × R_conductor / (2 × Z₀) [dB/m, approximate]. With Resistance per Meter 1.1, Characteristic Impedance 0.47 kΩ, Loss per Meter works out to 0.01016.

What is the formula for Coaxial Cable Loss?

The formula is α ≈ 8.686 × R_conductor / (2 × Z₀) [dB/m, approximate]. Coaxial cable attenuation is dominated by conductor losses at lower frequencies and dielectric losses at higher frequencies.

How do you find Resistance per Meter when you know the other values?

Rearrange for Resistance per Meter: with Loss per Meter 0.025, Characteristic Impedance 1 Ω, Resistance per Meter is 0.005756.

How do you find Characteristic Impedance when you know the other values?

Rearrange for Characteristic Impedance: with Loss per Meter 0.025, Resistance per Meter 0.055, Characteristic Impedance is 9.555 Ω.

Related Concepts

All Wire & Cable formulas →
Wire Resistance AWG to Cross-Section Area Cable Voltage Drop Maximum Cable Length Skin Effect AC Resistance Coaxial Cable Impedance Connector Contact Resistance Coaxial Cable Loss

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