Velocity of propagation is the ratio of the speed of an electric signal down a length of cable to the speed of light in free space, expressed as a percentage; it is the reciprocal of the square root of the dielectric constant of the insulation, and for coaxial cable with polyethylene dielectric it is about 65 to 66 percent.
Velocity of propagation is the ratio of the speed at which an electrical signal travels down a length of cable to the speed of light in free space, expressed as a percentage. Every insulated cable has such a ratio, and it is determined by the cable's insulation: specifically, it equals the reciprocal of the square root of the dielectric constant of the insulating material. A lower dielectric constant gives a higher velocity of propagation. For example, coaxial cables with a polyethylene dielectric have a velocity of propagation of about 65 to 66 percent.
Because the dielectric constant of the insulation sets this velocity, materials with low dielectric constants, such as foamed insulations, produce faster signal propagation. Velocity of propagation matters in high-frequency and timing-sensitive applications, where the speed and delay of signals along the cable affect performance.
In commercial and industrial systems, velocity of propagation is an important characteristic of coaxial and high-frequency cable, influencing signal timing and electrical length. Recognizing the concept helps in understanding how insulation affects signal behavior.
At Windy City Wire, an understanding of signal characteristics, including velocity of propagation, supports the selection of cable engineered for clean high-frequency performance. Recognizing how the insulation's dielectric constant sets the signal speed helps customers appreciate the characteristics relevant to their applications.