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Product Questions

Cable Delay Calculations

Calculating the propagation delay of coaxial cable

The delay of a cable or velocity factor is determined by the dielectric constant of the cable.  The velocity factor is the speed at which an RF signal travels through a material compared to the speed the same signal travels through a vacuum.  The velocity of propagation is inversely proportional to the dielectric constant.  Lowering the constant increases the velocity.  Generally, the higher the velocity factor, the lower the loss through a coaxial cable.  Said another way, Velocity of Propagation (VP) or velocity factor (VF) is a parameter that characterizes the speed at which an electrical signal (e.g. radio) passes through a medium.  Expressed as a number between 0 and 1 (or a percentage), it is the ratio of a signal's transmission speed to the speed of light in vacuum. Thus, transmission in a vacuum would have a VP of 1 (100%).  VP equals the reciprocal of the square root of the dielectric constant of the material through which the signal passes. 

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