Sky and space wave propagation

Sky and space wave propagation

Space wave propagation and skywave propagation are directly related to radio wave propagation. They are used to communicate at high and low frequencies.   To understand more about skywave propagation, space wave propagation, application of space wave propagation and space wave propagation limitations, we need first to understand its type. Let us also discuss electromagnetic waves and their characteristics of electromagnetic waves.

Radio Wave Propagation

Radio wave propagation also shows the medium through which they propagate and how radio waves are affected by that medium. 

Classification of radio wave propagation

1. Skywave propagation
2. Space wave propagation
3. Free space propagation
4. Ground wave propagation

What is sky wave propagation?

Skywave propagation is sent by the transmitter but gets reflected or refracted back towards the earth from the ionosphere. The ionosphere is an electrically charged layer of the upper atmosphere. To communicate beyond the horizon, skywave propagation is used. It is also used at an intercontinental distance and at shortwave frequency bands. Skywave propagation is also used for long-distance (DX) communication by directing waves at a low angle and relatively local communication. Skywave propagation is also known as skip wave. 

3MHz to 30MHz is the frequency of a radio wave that propagates using the ionosphere. The ionization density divides the ionosphere into three layers, L1, L2, and L3. L1 and L2 are weakly ionized by the sunlight falling into them, so they both transmit waves in the daytime. Depending on the sunlight reaching the molecules because of the ionization and formation of the ionosphere, the number of charged particles is more during the day and less at night. During the day and night, this is the reason for fluctuation in the signal transmission. L3 is again divided into two sub-layers and they can primarily refract the waves.

Skip Distance

It is the minimum distance between two points where radio waves are transmitted, refracted back from the ionosphere and received back at another point. From the earth’s surface, it is taken horizontally due to the minimum distance.

What is space wave propagation?

Space Wave Propagation is also directly related to radio wave propagation. The radio wave propagates from the transmitting antenna to reach a receiving antenna through the space around it, then the Space wave propagation takes place. The radio wave propagates either in the troposphere or after reflecting directly or from the ground.

It occurs within the range of 20km from the earth’s surface, i.e., the troposphere. Frequency ranging from 30MHs-300MHz(very high), space waves are used. The reason behind this is, the skywave propagation and ground wave propagation fail at a very high frequency. Two other names of space wave propagation

1. Tropospheric propagation
2. Line-of-sight propagation

1. Tropospheric propagation

The wave propagating directly from the earth’s surface to its tropospheric surface is known as tropospheric propagation.

2. Line-of-sight propagation

When a wave travels in a straight line and covers a minimum distance of sight, This is called Line-of-sight propagation. One can also see these waves with naked eyes.

Three components on which the space wave propagation depend

Space wave propagation depends on three parameters

1. Direct waves
2. Ground reflected waves
3. Tropospheric waves

Direct Wave

The waves directly reaching the receiving antenna from the transmit antenna are known as Direct waves.

Ground reflected wave

Reaching the receiving antenna after reflecting from the ground, the radio waves are known as ground reflected waves.

Tropospheric waves

Tropospheric waves are those waves that, after reflecting from the troposphere, radio waves reach the receiving antenna.

Applications of space wave propagation

Space wave mode of propagation can be useful in various systems like

1. Microwave linking
2. Television Broadcast 
3. Line-of-sight communication

Space wave propagation limitations

• The curvature of the earth affects these waves.
• Along with the line-of-sight distance, the propagation of these waves happens (range of communication or the distance between transmitting antenna and receiving antenna is known as line-of-sight distance).

What are Electromagnetic waves?

Electromagnetic waves are generated by the oscillation of electric fields and magnetic fields. In other words, we can say that the result of vibration between the electric field and the magnetic field is called EM or electromagnetic waves. 

When an electric field and a magnetic field come in contact or when they both combine with each other, they form electromagnetic waves. Thus, they are known as electromagnetic or EM waves. The electric field and the magnetic field of electromagnetic waves both are perpendicular to the direction of electromagnetic waves. Also, they both are perpendicular to each other.

3*108ms-1 in a vacuum is the constant velocity of EM waves at which they travel. Electromagnetic waves are not deflected by the electric field and the magnetic field. They can also show interference and diffraction. EM waves are measured by their wavelength and amplitude because they are transverse waves. EM waves do not need any medium to propagate or to travel from one place to another. EM waves can travel through any medium such as air, solid material or vacuum. “Crest” is the highest point of a wave and “trough” is the lowest point of waves. In the electromagnetic spectrum, the electromagnetic waves can spit into frequencies. Examples of Em waves are Radio waves, gamma rays, X- rays, microwaves and infrared waves, etc. Electromagnetic waves have also had some characteristics.

Characteristics of Electromagnetic waves

• While traveling from the source to load, the energy of the electromagnetic waves is wasted. The loss of energy is called the attenuation of electromagnetic waves. During the propagation, the energy is observed by trees, buildings and rivers. This is the reason why attenuation occurs.
• Throughout the propagation, the energy of the electromagnetic waves is equally distributed in the electric field and magnetic field. 
• If there is an electric field, then the magnetic field will also be there because they are related.

Conclusion 

Space wave propagation and skywave propagation both are essential for the propagation of waves. If everything has its application, then they will also have some limitations. This same applies to space wave propagation and  many scientists have given different theories about sky waves and space waves and also about electromagnetic waves. There are different types of electromagnetic waves, which have been explained above. These waves play an essential role in sending and receiving signals. Electromagnetic waves have their own applications, which are also explained above. Electromagnetic waves are a little different from sky waves and space waves propagation.