Coax Cable Loss Calculator

Coaxial Cable Loss Explained

Signal loss in coaxial cable comes from two primary mechanisms: conductor loss (resistive heating in the center conductor and shield) and dielectric loss (absorption in the insulator between the conductors). Both increase with frequency, which is why cable selection becomes critical at higher frequencies.

Loss Mechanisms

• Conductor loss: Proportional to the square root of frequency. Caused by the skin effect, where RF current flows in an increasingly thin layer on the conductor surface as frequency increases.
• Dielectric loss: Proportional to frequency. Caused by molecular reorientation in the insulating material. PTFE (Teflon) dielectrics have the lowest loss; foam PE is intermediate; solid PE has the highest.
• Radiation loss: Negligible in properly shielded cables, but can become significant with damaged or poorly terminated connectors.

Cable Selection Guidelines

• Below 100 MHz: Most cables work well. RG-58 is adequate for short runs. Cable selection is less critical.
• 100 MHz to 1 GHz: Use LMR-240 or better for runs over 10 feet. RG-58 loss becomes significant.
• 1 to 6 GHz: LMR-400 or equivalent is recommended. RG-142 (PTFE) for applications requiring flexibility and temperature resistance.
• Above 6 GHz: Consider semi-rigid coax or waveguide. Flexible cable losses become prohibitive for most applications.

Formula