All the relevant waves are electromagnetic waves. Sound waves are converted. Carrier waves are generated either in the phone or the transmitter (depending on which way the information is flowing). The carrier wave is an EM wave which has the characteristic of being able to travel sufficient distances (usually in the microwave region). The sound wave which is converted to an EM wave is then embedded in the carrier wave. Once it reaches its destination the carrier wave is stripped off.
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One way of doing it is Frequency Division Multiple Access (FDMA) : FDMA separates the spectrum into distinct voice channels by splitting it into uniform chunks of bandwidth. Each call sends its signal at a different frequency within the available band per geographical cell. But there are other ways with digital communications. Wikieducator has a good pdf piece on cell phone technology.
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If you embed a signal within a carrier wave then there is a degree of uncertainty about the precise wavelength of the carrier wave. That uncertainty is really the bandwidth. It is the amount of the spectrum that is taken up to cover all the frequencies needed to be included in the signal such that there will be no interference with the signal embedded in a neighbouring carrier away
Very nice video covering a lot of good information. I detail: the AM modulation you are drawing is not quite like that in normal AM, what you have drawn is side band modulation where no effect is transmitted when the modulation signal is 0 v. With normal AM, the carrier voltage is half its max when modulation signal is at 0 V.
Great video, thank you! What do you mean when you talk about the bandwidth of the AM wave because you say that the amplitude is 20kHz but I thought amplitude was measured as a distance?
If the power of a mobile is so low, how can be possible for an receiver to get the signal from a mobile phone? can you make a video about it ? Thanks !!
Hi i just don't quite get the bit about bandwidth, how come if you reduce the bandwidth leading to higher frequencies lost, that will reduce the quality of transmitted signal?
The question now is why is there a bandwidth for AM. If I am merely manipulating my carrier wave's amplitude with respect to the signal, it's frequency should remain unchanged, right? Or am I getting something wrong here?
please tell me from where the carrier waves are transmitted??from a radio station?and how does the information signal attatch on the radio carrier waves??and the informaton signal refers to the sound waves??
Is it really how ADC works? I mean to represent a wave with a certain amplitude in analog, it takes several waves to represent the same wave in digital... Which is the reason "you loose information density by converting from analog to digital"... Or am I missing something? I am referring to 16:50
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First of all thank you sir for this wonderful explanation of Telecommunication I have one doubt here that if you are telling that for sending message to far distance we have to modulate it at higher Frequency But On the other hand FM (Which operates at higher frequency) travels less distance as compared with AM (Which operates at lower frequency) Why is it so can you please clarify that???
Thank you Sir for the wonderful you tube. please give me detail explanation how is Microwave auditory effect this is what I mean microwave hearing, is modulated using satellite.
Is the carrier-wave digitalized too (before transmission)? And how does a digital signal move the electrons in the antenna (to create the EM-radiation)?
No. The carrier wave is just a straightforward Electromagnetic wave in the microwave region or radio wave region. There is no signal in it to digitise until you add the signal itself either in analog or digital form.
Animation The difficulty is that a lot of the time there is talk about waves, where in fact it's just signal-processing. The only real waves are the incoming soundwave and the outgoing radiowave; inbetween there is no wave.
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