Sky and space wave propagation

Electromagnetic waves, often referred to as electromagnetic radiations, can be described in terms of overlaid waves of an electric field and a magnetic field within space with the directions of propagation parallel to each other. In simple terms, electromagnetic waves are the result of oscillations by electric and magnetic fields.

The direction of propagation of these waves is parallel to the direction of the force in one of these fields. Like all waveforms, they are not without their own properties. Let’s take a look at the characteristics associated with electromagnetic propagation.

Properties of Electromagnetic Wave Propagation

• These waves move at speeds that are comparable to the speed of light.
• The waves don’t require any kind of medium to propagate.
• Electromagnetic waves are transverse in nature.
• Electromagnetic waves can’t be affected by magnetic or electric fields.
• The waves can be transformed into polarised waves.
• Electromagnetic waves can be affected by diffraction and interference.

It is possible to determine the wavelength (λ) and the frequency (v) of EM waves in the following way:

c= v.λ

Where the c is the velocity of the wave. To analyse the electromagnetic wave’s propagation, take a look at the example of the X-rays production.

X-rays are electromagnetic waves with an amplitude range of 0.001 nanometers up to 10-nanometers (1 nanometre equals to 10-9 metres). They are used for a range of applications, from medical, such as the detection of an abnormality within the body, to security in airports and public spaces.

X-rays are created within an X-ray tube, which has the vacuum of an enormous potential difference between its ends. It creates the electrons to travel at high speed to reach the target anode, which is usually the metal tungsten, or another depending on the wavelength that is required.

When electrons come into contact with the target, they transfer the huge energies they have in the form of photons back to the anode, thus creating X-rays. We will now study ways of transmission in EM waveforms: Mesosphere, Troposphere, Ionosphere are the three layers.

These layers are employed to propagate EM waves. EM waves are propagated via any one of the two techniques discussed below:

Sky Wave

It is used to propagate EM waves that have frequencies ranging from 3-30 MHz. In the ionosphere, the charged ions exist within the range of 60-300 km from the surface of the Earth. These ions serve as a reflection media for radio communication signals within a specific frequency range. This property is used by the ionosphere to transmit long distances of waves with minimal diminution in signal strength.

A further important aspect to take note of is the importance of observing the angle at which the emitter of the waves from below. The transmitter emits EM waves at a certain angle to ensure they reflect towards the ground, just as the complete internal reflection of optical waves; otherwise, the waves could escape into space. It is the difference between the two points where the waves are transmitted.

Space Wave

It is used for line of sight communication, commonly referred to as LoS. Space satellite communications and extremely high-frequency waves utilise this technique of propagation. It is basically about sending signals in a straight path from the source to the recipient. It is essential to ensure that, for extremely long distances, the tower’s height utilised for transmission is high enough to keep waves from reaching the earth’s curvature, which prevents attenuation and loss in signal quality.

Applications of Space Wave Propagation

The applications of space wave propagation are:

• Microwave linking
• Radar communication
• Satellite communication and line of sight communication

Applications of Sky Wave Propagation

The applications of sky wave propagation are:

• Satellite communication
• Mobile communication

Sky Wave Propagations Limitations

The Sky wave propagations limitations are:

• Large-sized antennas required for propagating through long distance
• Variation in signal transmission due to ionosphere presence

Space Wave Propagations Limitations

The space wave propagations limitations are:

• Space wave propagations occurs along the sight distance line, which is the range of communication, also referred to as the distance between the transmitting and receiving antenna
• The curvature of the earth affects the waves

Conclusion

The sky waves are radio waves that range from 2MHz and 30MHz. The ionosphere reflects these radio waves so that they are able to propagate through the air. Skywave propagation is often referred to as ionosphere propagation. The skies waves are utilised to provide radio communications that are very long distance with medium-high frequency, i.e., medium waves as well as short waves. Radio waves can travel an area of approximately 400 kilometres in one reflection of the ionosphere.

Space waves are radio waves that are extremely large in frequency, i.e., between 30 MHz and 300 MHz or greater. Space waves traverse the atmosphere to form an antenna for transmission to receive an either directly or following reflection from the ground in the troposphere region of the earth. It is also known as Tropospheric propagation or as a line of sight propagation. The propagation is restricted to the distance along the line of sight. It is also limited by the curvature of the earth. It is employed to transmit T.V. communication, radar communication, etc.