velocity factor การใช้

• In electrical cables, the velocity factor mainly depends on the insulating material ( see table below ).
• Some typical velocity factors for radio communications cables provided in handbooks and texts are given in the following table:
• The velocity factor likewise applies to antennas in cases where the antenna conductors are ( partly ) surrounded by a dieletric.
• In a medium ( other than vacuum ), velocity factor or refractive index are considered, depending on frequency and application.
• For both forms ( pipe or paint ), the length is dependent on the velocity factor for the outer transmission line.
• For example, a typical velocity factor for coaxial cable is . 66, corresponding to a dielectric constant of 2.25.
• Transit time on a 1 meter cable is about 5 ns 3.33 ns with adjustment for velocity factor-- >.
• Regardless, any cable intended for radio frequencies will have its velocity factor ( as well as its characteristic impedance ) specified by the manufacturer.
• Applying the velocity factor of . 66, this results in a " physical " length of cable 1.67 m long.
• In the case of coaxial cable, where F = 1, the velocity factor is solely determined by the sort of dielectric used as specified here.
• The speed of radio signals in a vacuum, for example, is the speed of light, and so the velocity factor of a radio wave in a vacuum is unity, or 100 %.
• In a general science and engineering context, these terms would be understood to mean a true speed or velocity in units of distance per time, while " velocity factor " is used for the ratio.
• The ratio of the speed of the electromagnetic wave to the speed of light in free space is called the velocity factor, and depends on the electromagnetic properties of the conductor and the insulating materials surrounding it, and on their shape and size.
• Their velocity factors thus depend not directly on the permittivity of the circuit board material but on the " effective " permittivity \ epsilon _ \ text { eff } which is often specified for a circuit board material ( or can be calculated ).
• For example, at a frequency ? = 20 MHz ( free space wavelength of 15 m ) in a transmission line whose velocity factor is 2 / 3, the guided wavelength ( distance between voltage peaks of the forward wave alone ) would be ? = 10 m.