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Electromagnetic Radiation Light, Sound and Waves. We've won an award! Learn more. Close Physics Links Explorer Explore the links between different physics concepts. Even though it is not as widely used as it was in previous years in its basic format it can nevertheless still be found.
These form some of the main uses of amplitude modulation. However in its basic form, this form of modulation is being used less as a result of its inefficient use of both spectrum and power. In order that a radio signal can carry audio or other information for broadcasting or for two way radio communication, it must be modulated or changed in some way.
Although there are a number of ways in which a radio signal may be modulated, one of the easiest is to change its amplitude in line with variations of the sound.
In this way the amplitude of the radio frequency signal varies in line with the instantaneous value of the intensity of the modulation.
This means that the radio frequency signal has a representation of the sound wave superimposed in it. In view of the way the basic signal "carries" the sound or modulation, the radio frequency signal is often termed the "carrier". From the diagram, it can be seen that the envelope of the signal follows the contours of the modulating signal. Amplitude modulation, AM, is one of the most straightforward ways of modulating a radio signal or carrier.
It can be achieved in a number of ways, but the simplest uses a single diode rectifier circuit. Other methods of demodulating an AM signal use synchronous techniques and provide much lower levels of distortion and improved reception where selective fading is present. One of the main reasons for the popularity of amplitude modulation has been the simplicity of the demodulation.
It enables costs to be kept low - a significant advantage in producing vast quantities of very low cost AM radios. As with any technology there are advantages and disadvantages to be considered. The summary below gives a highlight of the basic pro's and con's.
Although in the current technological climate, AM in its basic form is not nearly as effective as other modes that can be used, it is still retained in many areas like broadcasting, because of the number of users. However, it is likely that with time, its use will decrease still further and ultimately many AM transmissions will cease. However, its derivatives like quadrature amplitude modulation are widely used as they offer a very effective form of modulation, espceially for data transmission.
Although the use of amplitude modulation is decreasing, it nevertheless forms the basis of other forms of modulation that are still being widely used, or their use is increasing. AM has advantages of simplicity, but it is not the most efficient mode to use, both in terms of the amount of space or spectrum it takes up, and the way in which it uses the power that is transmitted. This is the reason why it is not widely used these days both for broadcasting and for two way radio communication.
Even the long, medium and short wave broadcasts will ultimately change because of the fact that amplitude modulation, AM, is subject to much higher levels of noise than are other modes. For the moment, its simplicity, and its widespread usage, mean that it will be difficult to change quickly, and it will be in use for many years to come. Amplitude modulation history The first amplitude modulated signal was transmitted in by a Canadian engineer named Reginald Fessenden. Amplitude modulation applications Amplitude modulation is used in a variety of applications.
Broadcast transmissions: AM is still widely used for broadcasting on the long, medium and short wave bands. It is simple to demodulate and this means that radio receivers capable of demodulating amplitude modulation are cheap and simple to manufacture. Nevertheless many people are moving to high quality forms of transmission like frequency modulation, FM or digital transmissions.
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