Secondary Line Constants
There are the following secondary line constants.

Propagation Constant
Propagation constant is one of the secondary line constant which represents that in which manner the propagation take placed along the transmission line. It is denoted y the letter γ Gama.
Formula
1. γ = α + Jβ
α stands for attenuation constant
β stands for phase shift constant.
2.
Here y stands for admitance and z stands for impedance of transmission line

Attenuation Constant
It is the type of secondary line constant which represents the reduction or attenuation in the voltage and current along the transmission line. It is abbreviated as α Alpha and its unit is Neper/km.
Formula
α = R/2z Neper/km
1 Neper = 8.686 αβ

Phase Shift Constant
It is the constant which represents the change in the phase of voltage and current along the transmission line. It is abbreviated as β and its unit is radian/km.
Decibel
1 Radian = 57.3 dB
Formula

Phase Velocity
The phase velocity represents the velocity of electromagnetic waves through the transmission line. It is denoted by V_{p}. The velocity of E.M waves in free space is 3 X 10^{8} m/sec. other than the free space when the propagation of E.M waves take place. Its velocity decreases. It never exceeds then the velocity of light.
Formula
V_{p} = λf km/sec
V_{p} stands for Phase Velocity
λ stands for wavelength
f stands for frequency of E.M waves.

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Velocity Factor
It is the ratio between the velocity of electromagnetic waves in free space and other mediums along transmission line. It is denoted by V_{f}
Formula
V_{f} = V_{L}/V_{C}
Here V_{f} stands for velocity factor.
V_{L} stands for velocity of electromagnetic waves in other medium
V_{C} stands for velocity of electromagnetic waves in free space.

Wave Length
The wave length can define by the following ways.
 The distance covered by one cycle of the wave travelling along the transmission line is known as wavelength for that frequency the E.M waves
 The distance between two success peaks of the positive half cycles or negative half cycle along the surface of the transmission line is known as wave length.
 The 360 degree complete revolution along transmission line for the electromagnetic waves is called its wave length.
 The distance covered by 2π radius when its phase changes along the transmission line is called the wave length of the E.M wave for that particular frequency.
λ = 2π/β meter
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