The velocity factor in an RF transmission line is determined by:

The velocity factor in an RF transmission line is indeed determined by the dielectric material between the center conductor and the shield. The velocity factor is a measure of how fast a signal travels through a medium compared to the speed of light in a vacuum. It is influenced primarily by the dielectric properties of the insulator surrounding the conductors.

Different materials have varying dielectric constants, which affect how quickly electromagnetic waves can propagate through them. A higher dielectric constant typically results in a lower velocity factor, meaning the signal travels slower relative to the speed of light. This relationship is crucial for understanding signal integrity and performance in RF applications, as it directly impacts the impedance and attenuation of the transmission line.

Other factors, such as the material of the center conductor or the transmission line's length, do not directly affect the velocity factor itself. The frequency of the signal also does not determine the velocity factor; rather, it may influence the overall behavior of the transmission line, such as losses and impedance, but the inherent speed of the signal propagation remains linked to the dielectric used.