Why do radio stations use modulation (AM/FM) instead of just using Electromagnetic waves?
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Because we'd all get cooked
362672
Radiowaves, look it up.\nAnd you definately got the category wrong.
397877
Many analogue TV cards can also pick up FM radio. You can also purchase computer mice that work the same way. However, depending on what you want to listen to, many radio stations also broadcast over the web, which means if you have broadband you wouldn't need to buy any extra equipment.
854524
Radio frequency, or RF, refers to that portion of the electromagnetic spectrum in which electromagnetic waves can be generated by alternating current fed to an antenna
74707
What you hear is 1K (1000kilohertz) signal.  Broadcasters use that tone to adjust equipment.  So it's handy and has been used since the beginning.  A few years back it also used to be used for the Emergency Broadcast System.
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Every station has a transmitter that radiates radio signals around its area. A lot of the signals reflect off the atmosphere, and this along with the power of the transmitter determines how much area the signal covers.\n\nHow the transmitter sends out a radio signal?\n\nThere's an excellent in-depth discussion on Wikipedia (the link I provide), but I copy here the one important point:\n\n"In principle any conductor (wire) carrying an alternating current will radiate a radio signal. Thus a basic transmitter is just an oscillator connected directly to a wire antenna."\n\nSo you need a conductor with an alternating current going through it. This will send out radio waves. Of course, its more complex if you want the radio signal to contain a voice or song broadcast of course.\n\nRemember that a radio wave is just another type of electromagnetic radiation, along with xrays, and light. The only thing that seperates light and radio is the wavelength (def: every oscillating electromagnetic signal has a property that specifies the distance from one peak of the signal to the next) of the radiation. \n\nOur eyes are basically receivers that can interpret electromagnetic radiation within a certain range. So think of radios as a type of artificial eye that reacts to radio signals, and that a radio station is basically one huge flashlight.\n\nThat's as simple an analogy I can make.
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All radio transmissions can be considered analog even the digital ones like FSK, PSk,QAM, since the carrier is sinsoidal which is analog, however the data are digital so they change the carrier characteristic in discrete way. in mobile systems such as GSM the type of modulation is GMSK (gausian minimum shift keying), which is a special type of FSK (frequency shift keying), in FSK the frequency of the carrier is alternating between two values, each frequency represents a logic state (digital), which can be processed by the mobile circuitry. again the FSK is an FM signal whith the message being digital (binary)
40144
I guess you know that am radio reception is altered when you rotate your radio. To increase reception you have 2 alternatives. Either get a longer antennae (you can use the same antennae that you use for your tv regular,cable or satelite) or you can get a am reception booster from Radio Shack that electronically sucks in better reception but plan "A" works best.
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you can use a fm modulator
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The main concept to understand is that of a carrier wave.  The radio wave is that.  A radio wave is electro-magnetic radiation, which, unlike other waves, is not a vibration within a medium, like sound waves for example, which are the propagation of alternating high and low pressure within the air, or other fluid media.  Electro-magnetic waves are a self propagating electro-magnetic effect which can travel even in a vacuum.  Electro-magnetic radiation is a pulsing stream of energy where the pulses are at a constant frequency.  What we perceive as different phenomenon are in fact the same electromagnetic radiation but at different frequencies.  Microwaves, Radio, Ultra-violet, Visible Light, and Infra-red, are all electro-magnetic radiation moving down the scale from high to low frequency.\n\nThe radio transmitter sends out radio waves at a specific frequency or band of frequencies.  The aerial of the receiver develops tiny electric currents in it as the radio wave flows past it.  These are pulsing currents at the same frequency as the radio wave, but these pulses are not in themselves the content of speech or music.  This content, or signal, is carried in the wave, hence the concept of the carrier wave.\n\nIt is easier to understand Amplitude Modulation or AM radio so I will restrict myself to that.  If you imagine a radio wave as a very long string with the pulses like beads on it, all spaced at precise intervals, then imagine that the beads slowly getter bigger and smaller along its length.  Each bead is a packet of energy in the wave and all occur at the same frequency, but where the beads get bigger there is more energy in the packet.  It only takes a little more imagination now to see how the pattern of a sound wave can be represented by the bulging out of the beads, and their getting smaller.  This is called the amplitude.\n\nLooking at it in practical terms, at the transmitter end sound is converted in the microphone into a corresponding pattern of changes in the current flowing through the microphone.  That is your signal.  That signal which is at a low electrical power, is used to create the same pattern but in a circuit of much higher electrical power - that is what an amplifier does.  The device used to transfer the pattern is called a transistor, which uses the low powered circuit to control the flow in the high powered circuit.\n\nThe amplified signal is fed to the transmitter aerial, so now that pattern of electrical energy, identical to the pattern of the sound picked up by the microphone, comes out of the aerial as radio waves, with the pattern held in the varying amplitude of the radio wave.\n\nNow comes a trick to follow.  If there are thousands of transmitters all radiating radio waves all over the place, how come your radio only picks up the one signal.  This is where the tuner comes in.  The principle of radio tuning depends on the opposite properties of coils and capacitors.  I don't know if you know what these are, but it doesn't matter if you don't.  Both of these devices have a special kind of resistance to electricity known as impedance.  Impedance only operates where the current is varying.  The voltages and currents in our radio Ariel will be varying at exactly the same frequency as each radio wave it is exposed to, so if we pass that current through either a coil or a capacitor there will be an impedance in the circuit.  Now the impedance of the coil increases as the frequency gets higher and the impedance of the capacitor gets higher as the frequency gets lower.  An AM tuning circuit simply passes the signal current through both a coil and a capacitor at the same time, and the capacitor is a mechanically variable one, so by turning a knob you can increase or decrease the capacitance.  The trick here is that as the capacitance changes the circuit will show least impedance to a specific frequency compared with all the others, so provided the frequencies are not too close, as the law requ
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Electromagnetic waves don't need medium to travel.\n\nLike light, radio too, is an elctromagnetic wave, so it can travel through vacuum.
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Frequency modulation, called FM, is a more sophisticated modulation scheme than AM modulation. It is well-suited to the inherent properties of optical fiber since proper recovery of the encoded signals only requires measurement of timing information, one of fiber’s strengths. FM is also immune to amplitude variations caused by optical loss, one of fiber’s weaknesses. The heart of the FM modulator revolves around a high-frequency carrier. Now, instead of changing the amplitude of the carrier, the frequency of the carrier is changed according to differences in the signal amplitude. Part of the advantage of FM systems is buried in mathematical analyses that show that the signal-to-noise ratio at the receiver can be improved by increasing the deviation of the carrier. \n\nFM also has the advantage of eliminating the need for highly linear optical components that are required for AM systems. Often optical systems employing FM encoding refer to the technique as pulse-frequency modulation (PFM). This simply means that the FM signal is limited (converted to digital 0’s and 1’s) before it is transmitted over the fiber. The result is the same. In multiple channel FM systems, each video signal is modulated on a separate carrier. These carriers are then combined to modulate one light source. Each FM video modulator is adjusted to balance distortion products, achieve best signal-to-noise/bandwidth plus compensate for the non-linearity of the light source. As more video channels are added, the overall modulation index of the combined signal increases, which degrades the per channel signal-to-noise ratio (i.e., there is less optical power available per channel.) \n\nFrequency modulation uses the information signal, Vm(t) to vary the carrier frequency within some small range about its original value. Here are the three signals in mathematical form: \n\nInformation: Vm(t) \nCarrier: Vc(t) = Vco sin ( 2 p fc t + f ) \nFM: VFM (t) = Vco sin (2 p [fc + (Df/Vmo) Vm (t) ] t + f) \n\n\nand if u get the below article whole funda be resolved
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It can't really. The key here is 'information' and information is different from data. The thing is that the data you are sending doesn't contain as much information as you think it does. In other words it can be compressed. So the data you can cram down a phone line is first compressed and then sent in a way that makes the absolute best possible use of the available bandwidth. \n\nit's not worth going into the details of the modulation techniques, in the end they all require a small change in the signal to pass a bit of compressed data and that requires bandwidth. There's no magic in this, just clever physics and software.\n\n(n2thepowerofn below) Lol!
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Many of them are, it depends on the wavelentgh.  Shorwave radio uses the atmosphere to bounce the waves back to earth giving it a range of over 1/2 the planet.  Other wavelenghts make it though and others are absorbed.\n\nOn another note, visible light, UV light, IR waves are all electromagnetic waves and make it through one way, it all depends on the energy of the wave (wavelength/frequency)
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Radio waves are a form of electromagnetic radiation, created whenever a charged object (in normal radio transmission, an electron) accelerates with a frequency that lies in the radio frequency (RF) portion of the electromagnetic spectrum. In radio, this acceleration is caused by an alternating current in an antenna. Radio frequencies occupy the range from a few tens of hertz to three hundred gigahertz, although commercially important uses of radio use only a small part of this spectrum.[1]\n\nElectromagnetic radio spectrum \n\nOther types of electromagnetic radiation, with frequencies above the RF range, are microwave, infrared, visible light, ultraviolet, X-rays and gamma rays. Since the energy of an individual photon of radio frequency is too low to remove an electron from an atom, radio waves are classified as non-ionizing radiation.\n\nMobile phones and the network they operate under vary significantly from provider to provider, and even from nation to nation. However, all of them communicate through electromagnetic radio waves with a cell site base station
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Both B and G devices operate in the 2.4GHz frequency band.  However G uses a more advanced modulation technique which gives it higher throughput and better range than B.  A uses the same modulation technique as G but it operates in the 5GHz frequency band.  Higher frequencies don't penetrate obstacles as well, so A has a shorter range.  However in environments where a lot of 2.4GHz devices are in use (wireless phones, microwaves, 802.11b/g), A is preferable.  Also A devices are capable of using more channels so you can use more A devices in an area than B or G devices (not really important for the home user).
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Satellites use non-linear amplifiers to relay signals back to earth.  Using AM for any type of transmission through the satellite would heavily distort the AM signal and make the signal have very poor quality.\n\nVideo, or more accurately TV signals used to be exclusively distributed via satellite using FM because of its constant envelope characteristic made them largely impervious to the amplitude distortions caused by the non-linear amplification of the satellite.  \n\nHowever, increasingly more video (TV) transmissions are using digital transmission schemes.  Here the baseband TV signal is digitized into some bit format and the bits are used to phase-modulate (PM) the carrier. When PM is digitally modulated it is known as Phase Shift Keying or PSK. This also has a constant envelope characteristic like FM and PM making it suitable for the non-linear amplification of the satellite.\n\nSatellite amplifiers are becoming more and more powerful as the technology improves.  They also are becoming more linearized.  This is allowing digital transmissions to utilize a combination PSK and AM technique known as APSK or sometimes, QAM (Quadrature Amplitude Modulation).  Using these techniques requires the satellite amplifiers to be used at much less than their full power, so they are linear and do not cause large amplitude distortions.  This is done because these newer techniques allow more bits/sec to be transmitted on the satellite channel.  This allows higher quality video (HDTV for example) or just more video signals per satellite channel.