PROPAGATION OF ELECTROMAGNETIC WAVES PART 01

Summary

This video discusses the propagation of electromagnetic (EM) waves used in communication, focusing on radio waves. It explains how an antenna at the transmitter radiates EM waves, which travel through space to the receiving antenna. The video covers the effects of the Earth's atmosphere on wave propagation, including the impact of ground waves, sky waves, and ionospheric reflection. Different modes of propagation such as surface wave and skywave are highlighted, with emphasis on how the Earth's surface and ionosphere affect signal strength and range. The script also touches on the ionosphere's role and its layers in communication systems.

Takeaways

• 😀 Electromagnetic (EM) waves are used for communication, with radio waves being a primary example.
• 😀 The transmission of EM waves involves an antenna at the transmitter radiating waves, which travel through space to the receiving antenna.
• 😀 The strength of the EM wave decreases as it travels away from the transmitter.
• 😀 Several factors influence the propagation and path of EM waves, including the composition of the earth's atmosphere.
• 😀 Antennas should be approximately λ/4 in size to radiate signals efficiently, where λ is the wavelength of the signal.
• 😀 At lower frequencies (longer wavelengths), antennas are larger and located closer to or on the ground.
• 😀 For standard AM broadcasts, ground-based vertical towers are used as transmitting antennas, which interact with the ground during signal propagation.
• 😀 The surface wave propagation mode involves the wave gliding over the Earth's surface, with energy being absorbed by the ground.
• 😀 The attenuation of surface waves increases significantly with frequency.
• 😀 Skywave propagation, involving ionospheric reflection, is used for long-distance communication in the frequency range of a few MHz up to 30–40 MHz.
• 😀 The ionosphere, composed of ionized particles, extends from about 65 km to 400 km above the Earth's surface and plays a key role in skywave propagation.

Q & A

What is the primary role of an antenna in communication using radio waves?

An antenna's primary role in communication is to radiate electromagnetic (EM) waves at the transmitter and receive them at the other end, enabling the transmission of signals.

Why does the strength of the electromagnetic wave decrease as it moves away from the transmitter?

The strength of the EM wave decreases due to the spreading of the wave as it travels through space, as well as energy losses in the atmosphere and ground.

How does the Earth's atmosphere influence the propagation of electromagnetic waves?

The Earth's atmosphere influences the propagation of EM waves by affecting the way they travel, including absorption and reflection, which alters the signal strength and the propagation path.

Why should antennas be sized relative to the wavelength of the signal?

Antennas need to be sized comparable to the wavelength of the signal to radiate efficiently. Typically, this means the antenna should be around one-fourth the wavelength of the signal.

What is surface wave propagation, and where is it commonly used?

Surface wave propagation occurs when a wave travels over the surface of the Earth. It is commonly used in AM radio broadcasts, where ground-based vertical towers serve as transmitting antennas.

How does the ground influence the propagation of electromagnetic waves in surface wave propagation?

The ground affects surface wave propagation by absorbing energy from the wave, which causes attenuation and limits the distance the wave can travel.

Why does attenuation increase with frequency in surface wave propagation?

Attenuation increases with frequency because higher frequency waves experience more absorption by the Earth's surface and atmosphere, leading to greater energy loss.

What is skywave propagation, and how is it different from surface wave propagation?

Skywave propagation occurs when radio waves are reflected off the ionosphere, enabling long-distance communication. Unlike surface wave propagation, which travels over the Earth's surface, skywave propagation involves the reflection of waves back towards Earth from the ionosphere.

What is the role of the ionosphere in skywave propagation?

The ionosphere plays a crucial role in skywave propagation by reflecting radio waves back towards Earth. It is made up of charged particles, which reflect waves at certain frequencies.

What is the frequency range for skywave propagation, and why is this range significant?

Skywave propagation is most effective in the frequency range from a few MHz up to 30-40 MHz. This range allows radio waves to be reflected by the ionosphere for long-distance communication, particularly in shortwave broadcasting.