Velocity Factor Calculator

Velocity Factor (VF) describes the speed at which a radio signal travels through a transmission line, expressed as a fraction of the speed of light. It’s used to determine how long a cable should be when building matching stubs, quarter-wave sections, or phasing lines.

The formula for velocity factor is: \[ \text{VF} = \frac{\text{Electrical Length}}{\text{Physical Length}} \] For example, if a 10-meter coax cable appears electrically as 6.6 meters, then VF = 0.66.

Typical VF values:

Foam dielectric coax: ~0.82 to 0.88
Solid polyethylene coax: ~0.66
Open wire line: ~0.95

This calculator can compute either the VF or the effective electrical length based on known values.