Effect of weather on radio transmission Weather affects the transmission of AM stations but does

Effect of weather on radio transmission Weather affects the...

Key Concepts

Radio Wave Propagation

This concept covers how electromagnetic waves travel through different mediums, including air. It explains that radio waves can be affected by barriers, the curvature of the Earth, and atmospheric conditions. Depending on their frequency and wavelength, radio waves may travel as ground waves or sky waves, determining their range and susceptibility to interference.

Wavelength and Frequency Effects

Longer wavelengths, typically associated with lower frequencies, are more likely to bend around obstacles and follow the curvature of the Earth, but they can be more influenced by ionospheric conditions and weather changes. In contrast, shorter wavelengths, found in higher frequencies, predominantly travel in straight lines (line-of-sight), and are less prone to interference from atmospheric disturbances.

Modulation Techniques (AM vs FM)

Amplitude Modulation (AM) encodes information in the amplitude of the radio wave, making it more vulnerable to noise and amplitude variations caused by weather phenomena. Frequency Modulation (FM) encodes information in the frequency of the signal, which tends to be less affected by variations in the amplitude, though it requires a clear line-of-sight and is constrained by its transmission range.

Atmospheric and Weather Effects

Weather can alter the propagation paths of radio waves through changes in temperature, humidity, and atmospheric density. These changes can affect the refractive index of the air, leading to bending, scattering, or absorption of the waves, which particularly impacts AM signals that rely on amplitude continuity for proper reception.

Transcript

00:01 Hello, everyone.

00:01 This is a solution to problem 50, chapter 24 off college physics.

00:05 Here we are asked to find out a few things about radio waves, namely waves off the am and fm bands off radius signals.

00:18 So just a quick google search reveals that the frequency range for am radio signals is between 540 times 1030 .3 hertz or 540 kilohertz.

00:30 And 1 ,600 times 1030 3 hertz or 1 ,600 kilohertz.

00:36 So the interesting thing about am waves is that they transfer information or sound information through electromagnetic radiation in a form where the amplitude of the wave is modulated.

00:54 And that's what am stands for, it's amplitude modulation.

00:57 So what happens is that there is a part of the equipment that produces the signal that creates a wave with a constant frequency and the given constant wavelength but then that signal becomes attenuated by an other part of the equipment that changes the amplitude and so the resulting wave that comes out of such an equipment is going to be of a given frequency and a given wavelength but it's amplitude is going to change, as you can see over here.

01:34 So basically, there is a carrier wave that's inside, which is of the same frequency, and then it has an envelope which changes the amplitude of the signal.

01:46 Now, the nice thing about these frequency ranges and these wavelength ranges is that they are very, or yeah, is that they are such that they get reflected from the ionosphere, so from the upper atmosphere.

01:59 Why that's good is that, this effectively allows you to project and transmit your signal very far away and effectively if you make the wavelength big enough all the way around the globe.

02:14 So if you have the surface of the earth here, for example, there is some batch of land, and then there's a radio signal that emits am waves or am radio signals.

02:25 Then the wave comes out and reaches the upper parts of the atmosphere, gets reflected, and then moves back down.

02:32 The earth.

02:33 But it doesn't only get reflected.

02:35 It also gets refracted.

02:37 And in such a case, the ionosphere can act kind of as a wave guide.

02:43 So you would have part of this wave reflecting back, but part of it would like kind of move around the atmosphere and it would be guided around the entire earth...

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