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Normal frequency range for amplitude modulation is 550kHz to 1610kHz
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∙ 15y ago
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Why you need modulation?
It might be helpful to have a working definition of modulation before making a statement as to why it is needed. In fact, with an understanding of what modulation is, it will be obvious why it is included in electronic communications.Modulation is the "message" or the "intelligence" that is impressed on a radio frequency (RF) carrier. When we transmit a signal, we generate a carrier frequency, and then we modulate it. We "add" the message or the information we wish to transmit by modulating the carrier in some way. There are at least a dozen different modulation schemes ranging from simple to real head scratchers. They either modify the amplitude, the frequency or the phase of the carrier. Let's look at a few.The simplest modulation technique is taking the transmitted signal and turning it on and off. It is "keyed" to send a series of pulses. Morse code uses on-off keying. In this method of modulation, no modification of the RF carrier signal itself is made. It is simply switched on and off. (It could be looked at as amplitude modulation with the carrier either at zero amplitude or at "maximum" amplitude with nothing in between.) A series of pulses can be transmitted. With Morse code, a short "on" period will send a dot or "dit" out. If we extend the "on" period a bit, we can send a dash or "dah" out. Nothing real sophisticated here, but basic and effective communication. There are obvious limits to how fast information can be transmitted with this modulation scheme. (But don't tell the hams who still use it!)Most of us are familiar with AM radio. AM is amplitude modulation. The amplitude of the RF carrier is modified to modulate it. The amplitude of the modulating signal will determine the amount that the amplitude of the carrier is changed. (The volume of the modulation determines how much the amplitude of the carrier is changed. The frequency of the modulating signal determines the rate of change of the amplitude of the carrier. (The frequency of the modulation determines how fast the amplitude of the carrier is changed.). The frequency of the carrier is held constant through all this.How about FM? In frequency modulation, the amplitude of the carrier is constant. It's left alone. But the frequency of the RF carrier is changed. It is swung above and below where it sits (it's assigned center frequency) at a rate proportional to the frequency of the modulating signal, and at an amount proportional to the amplitude of the modulating signal. In FM single sideband, the carrier frequency and the frequencies above the carrier are transmitted and the frequencies below the carrier are suppressed (upper sideband transmission). Or the frequencies below the carrier are transmitted with the carrier and the upper frequencies are suppressed (lower sideband transmission). In conventional television, the video signal is single sideband, suppressed carrier. It's like "regular" upper sideband transmission except the carrier signal is suppressed. Sideband transmission "saves" space on the RF spectrum. And it works because we really don't need "all" of the FM signal to demodulate the signal at the receiver.Other forms of modulation become more complex. CDMA (code division multiple access), TDMA (time division multiple access) and other methods are used in cell phones to modulate the carrier so the digital data stream can be impressed on the carrier.Modulation is the addition of intelligence to a carrier signal. It's the message. Modulation is necessary because the point of communication is getting the message through.A Simple answer:Simply this... Any communications medium: e.g. Free space - radio waves, Air - Sound waves or radio waves, Optical Fibre - Light, Copper Wires Electrical Anergy (with frequency limits of the copper wire construction) is made for a certain type of signal. But if the signal we want to send is not compatible with the medium, then it does not travel well.Modulation changes the information we want to send from it's original form, into one that is more compatable with the medium we are trying to use.For example, your computer speaks digital over a TCP/IP LAN which requires CAT 5 or better rated cables,, but to connect to your internet service provider (ISP), you need to send the signal over the wires of the telephone company (made for voice tones). To make this connection, and ADSL modem (modulator/demodulator) is used to convert the data into audio tones, which pass over the telephone line, and at the far end are converted back to digital to join the service providers network. in the reverse direct the ISP does the same, and the signals are de-modulated, back to data for your network.Or in simple terms, Its about best use of the medium. Everything else is just a away of doing it. And there are a lot of possible ways to choose.
What is the frequency range of video frequency oscillator?
5MHz
Difference between RF microwave?
RF means radio frequency or relativity low range of frequency microwaves however are into the top range of the spectrum or very hi frequency.
Why has the midi have a wide range of frequency?
i doesn't have the widest range the synthesiser does
What is transition frequency of a transistor?
The transition frequency of a transistor is the frequency in which the transistor will no longer provide any amplification or gain output. The frequency is out of the transistors's range.
What is the modulating frequency of amplitude modulation?
the frequency range of an am wave is 20herz to 20kilo herz
Frequency modulation range in India?
The frequency range of FM signal is 88hz to 108hz.
What are the contrast of amplitude modulation to frequency modulation?
AM (Amplitude Modulation) has a smaller bandwidth and can have more stations available in any frequency range. AM is cheaper and can be transmitted over long distances. FM (Frequency Modulation) signals are prone to interference due to physical obstructions. The better sound quality is due to a much higher bandwidth, using FM.
What is the modulation of frequency?
It is a device or electronic circuit that changes the frequency of an oscillator according to the amplitude of modulating signal. For instance, if the modulation is linear, the modulator changes the frequency proportional to the amplitude of the modulating voltage.
How does the intelligence signal modulates the carrier?
There are three major types of modulation:AM, Amplitude Modulation, where the modulation signal is altering the amplitude of the carrier according to its own amplitude, normally this is done in the output stage. Therefor a strong audio signal is necessary at the same or a little less than the power of the carrier, never higher, because that will over modulate the carrier that will resort in distortion of the receiver output. AM is used in the lower band of the RF spectrum.FM, Frequency Modulation, where the frequency of the carrier is altered by the audio signal. When the amplitude of the audio is going higher the frequency go lower. Modulation happen at the oscillator stage, therefor a small audio signal is used to modulate the frequency. FM is normally used in the higher frequency range of the RF spectrum, 50MHz and up.FSK, Frequency-shift keying, used for data transmission, this type of modulation is simply, switching the carrier on and of, a high bit will switch the oscillator on and a low bit will switch it off, in some designs a low will be on and a high off.
Why do you not use frequency modulation in long range transmission?
Frequency modulation is not used for long distance transmission because it has the problem of limited band width.
Why modulation is necessary?
modulation is necessary for transmitting low frequency signal to long range with desired qualitative information
Which is a property of light waves but not sound waves?
why cannot it be both? by definition, amplititude is the extreme range of fluctuating quantity. swing range of a pendulum, current flow,bla,bla,bla. amplitude MODULATION is in reference to radio waves with regards to signal RANGE ie: AM Radio- amplitude modulation am bounces and the range of frequency is modulated within the extreme band withs of the wave.
What are diffrence between AM radio waves and FM radio waves?
AM stands for "Amplitude Modulation". The sound signal you hear is transmitted by modifying the amplitude of the carrier frequency.FM stands for "Frequency Modulation". The sound signal you hear is transmitted by modifying the carrier frequency itself.AM uses a 5Khz bandwidth with additional space to allow for signal separation avoiding interference between stations.FM requires a wider bandwidth.AM has lower sound quality and is subject to static from weather conditions and adjacent frequency radio transmissions.FM has wider bandwidth per channel, due to the better ability to separate noise in the FM bandwidth.AM has a longer range than FM and with the correct conditions can bounce a signal off the ionosphere allowing for longer range possibly causing interference with far away radio stations on the same frequency.FM signals line of site only and will drop of after about 50 miles from the station as the earth curves away. To compensate for this, broadcasting stations use high transmission antennas.
What is the main use of frequency modulation?
Frequency modulation is used to broadcast radio waves to receivers. The most common use of it is in FM radio, which contains a range of radio frequencies.
How can you tell the difference between am and FM waves explain?
AM is an abbreviation for Amplitude Modulation, while FM stands for Frequency Modulation. Both are ways of transmitting information that can be decoded, usually into sound for radios. Basically, a wave has two properties that can be changed - amplitude and frequency, as you might have guessed. Amplitude describes how big a wave is. Larger amplitude sound waves are louder, and larger amplitude light waves are brighter. Frequency describes how long it takes a wave to repeat itself, and is the distance from one peak, the high point of a wave, to another peak; or from one trough, the low point of a wave, to another trough. Amplitude modulation means changing amplitude to encode information. All AM radio stations use this. It generally encodes less information than frequency modulation, producing a lower quality sound. As a consequence, AM stations tend to be talk shows. Also, the range of AM stations is much larger than that of FM stations. Frequency modulation means changing frequency to encode information. All FM radio stations use this. It usually encodes less information than AM, and can therefore produce a better quality sound. As such, FM stations are generally used to transmit music. The range of FM stations is lower than that of AM stations. The easiest way to tell the difference between AM waves and FM waves is the frequency. AM waves tend to be low frequency for radio, while FM waves tend to be much higher. You might think that FM waves would be hard to pin down, but the change in frequency is not very large, so that different stations don't interfere with each other. There is a lot more information on the subject, but this is a quick introduction.
Which modulation can reduce the noice of signal?
Signals of different frequencies cannot interfere with each other. For example can audio waves (speech) interfere with AM or FM signals?? So when we perform modulation we just transfer the message to another amplitude/frequency/phase. Hence they will never interfere with signals which are not in the same range as them. Regards Arvind
