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

The velocity factor in an RF transmission line is primarily influenced by the dielectric material that is situated between the center conductor and the outer shield of the cable. This factor represents the speed at which a signal travels through the transmission line relative to the speed of light in a vacuum.

The dielectric material affects both the capacitance and inductance of the transmission line, which ultimately alters the propagation velocity of the electrical signals traveling through it. For instance, different dielectric materials have different permittivity, which directly influences the velocity factor. Materials like air have a higher velocity factor compared to those with more substantial dielectric properties, such as polyethylene or teflon.

The length of the conductor primarily affects the total delay and attenuation of the signal but does not inherently change the velocity factor. Similarly, while the type of signal being transmitted could influence certain performance criteria in a transmission line, it does not determine the velocity factor, which is a characteristic of the physical construction of the line. Lastly, the temperature of the environment can lead to changes in resistance and other factors affecting signal integrity, but it does not affect the inherent properties of the dielectric material in relation to the velocity factor.

Thus, the dielectric material is the primary determinant of how fast signals travel through a given transmission