# Secondary Line Constants

There are the following secondary line constants.

1. ## 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

2. ## 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

3. ## 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 4. ## Phase Velocity

The phase velocity represents the velocity of electromagnetic waves through the transmission line. It is denoted by Vp. The velocity of E.M waves in free space is 3 X 108 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

Vp = λf   km/sec

Vp stands for Phase Velocity

λ stands for wavelength

f stands for frequency of E.M waves.

5. .

## 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 Vf

Formula

Vf = VL/VC

Here Vf stands for velocity factor.

VL stands for velocity of electromagnetic waves in other medium

VC stands for velocity of electromagnetic waves in free space.

6. ## 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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