Transmission Line Calculate Wavelength By Dielectric Constant

Do you want to know the true wavelength of those transmission line?

The true wavelength of a transmission line is the electrical wavelength, and not the physical wavelength of the transmission line. The electrical wavelength is depended on the velocity factor of the speed of light of the transmission line, and the velocity factor depends on what dielectric constant of insulated material between the 2 conductors of the transmission line.

Insulated material	Velocity Factor	Dielectric Constant
Polyethylene solid	66.7%	2.25
Teflon solid	70%	2.1
Polystyrene solid	60.8% to 64.5%	2.4 to 2.7
Polypropylene solid	65% to 67%	2.2 to 2.36
Polyethylene Foam	74 to 85% Depending on how much air bubbles in the foam.	1.38 to 1.8
Air	99.9%	1.00058986
Vacuum	100%	1

So the higher the dielectric constant of the insulated material of the transmission line, the lower the velocity factor, the shorter the electrical wavelength of the transmission line, and higher the loss per long length of transmission line. The lower the dielectric constant of the insulated material of the transmission line, the higher the velocity factor, the longer the electrical wavelength of the transmission line, and lower the loss per long length of transmission line.

To calculate velocity factor and transmission line electrical wavelength by dielectric constant:

Table of Definition
f =	Frequency in MHz (Megahertz)
l =	Electrical wavelength with the velocity factor of transmission line in feet.
VF =	Velocity factor of the speed of light of transmission line in percentage
k =	dielectric constant of the insulated material of the transmission line.

Dielectric constant is know as the Relative permittivity of AC or RF current through the insulated material in so many times the factor of conducting through vacuum, or unit of the dielectric material value between the 2 or more plates of the capacitor that would increase the value of a capacitor in so many times of vacuum insulation between 2 or more plates.

To calculate the velocity factor from a dielectric constant of the insulated materials of transmission line:

VF = 100 / Sqrt (k)

To convert it back to the dielectric constant from the velocity factor:

k = (100 / VF)²

To calculate the transmission line's electrical wavelength by dielectric constant:

l = 984 / (f x Sqrt (k))

To calculate the transmission line's electrical half wavelength by dielectric constant:

0.5l = 492 / (f x Sqrt (k))

To calculate the transmission line's electrical quarter wavelength by dielectric constant:

0.25l = 246 / (f x Sqrt (k))

To calculate the transmission line's electrical one eighth wavelength by dielectric constant:

0.125l = 123 / (f x Sqrt (k))