Cable Velocity Factors
Velocity Factor of Propagation Through Coaxial Cable (From Hamuniverse.com)
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.
Typical Velocity Factor Table:
General Rules for Coaxial Cable:
D = diameter of insulation under the shield
d = diameter of inner conductor.
Velocity Factor, Velocity of Propagation, Vp:
The higher the velocity factor, the lower the loss through the cable.
Raising the D/d has no effect on Vp
Raising the dielectric constant lowers Vp
Capacitance:
Raising the D/d ratio lowers capacitance
Raising the dielectric constant raises capacitance
Impedance Raising the D/d radio raises impedance
Raising the dielectric constant lowers impedance
Attenuation or Loss:
Raising the D/d ratio lowers attenuation
Raising the dielectric constant raises attenuation