What is characteristic impedance in coaxial cables?
Characteristic impedance is the ratio of voltage to current in a wave traveling along the cable. It depends on the cable's geometry and dielectric properties, typically 50Ω or 75Ω for most coaxial cables. See also our Twisted Pair Cable Calculator.
How does frequency affect coaxial cable loss?
Cable loss increases with frequency due to skin effect and dielectric losses. Higher frequencies experience greater attenuation, which is why shorter cables or cables with better specifications are needed for high-frequency applications.
What is the difference between inner and outer diameter in coax calculations?
Inner diameter refers to the center conductor, while outer diameter is the overall cable dimension. The ratio between these dimensions, along with the dielectric material, determines the cable's characteristic impedance.
What does relative permittivity (εr) mean?
Relative permittivity is the dielectric constant of the insulating material between conductors. Common values are 1.0 for air, 2.1 for PTFE, and 2.3 for polyethylene. Lower values generally result in better performance.
How do I minimize coaxial cable losses?
Use the shortest practical cable length, choose cables with lower loss specifications, ensure proper impedance matching, and select cables designed for your operating frequency range.
What is velocity factor in coaxial cables?
Velocity factor is the ratio of signal propagation speed in the cable to the speed of light in vacuum, expressed as a percentage. It depends on the dielectric material and typically ranges from 66% to 85%.
Why is impedance matching important?
Impedance matching between the cable and connected equipment minimizes reflections and signal loss. Mismatched impedances cause standing waves, reducing power transfer efficiency and potentially damaging equipment.
How accurate are these coaxial cable calculations?
These calculations provide theoretical values based on ideal conditions. Actual performance may vary due to manufacturing tolerances, temperature effects, connector losses, and cable bending or aging.