Velocity of Propagation

The Velocity of Propagation (VoP) is a measure of the speed at which a signal travels through a transmission medium, usually expressed as a percentage of the speed of light in a vacuum (approximately 3x108 metres per second). In a conducting material (e.g. copper), the VoP of a high-frequency electrical signal is equal to the reciprocal of the square root of the dielectric constant of the material:

The VoP for high-frequency electrical signals

Twisted pair copper cables typically have a VoP of between 40% and 75%. A VoP of 66% corresponds to a speed of approximately 2x108 metres per second.