0
There are two basic reason for modulation..... 1) It is extremely difficult to radiate low-frequncy signals from an antenna in the form of electromagnetic energy. 2)Information signals often occupy the same frequency band and if two or more sourses were transmitted at the same time they would interfere with each other.
Wiki User
∙ 15y ago
Wiki User
∙ 11y agoWiki User
∙ 13y agoThe purpose of radio communication is to move information from one place to another.
The carrier wave by itself carries no information. The information has to be added to it
somehow. When the electrical signal that carries the information is added onto the
carrier, that's the process loosely called "modulation".
Wiki User
∙ 13y ago"Modulation" is the process of changing the pure radio wave in some way,
for the purpose of causing it to carry information.
If a physicist on one side of the laboratory generates a radio wave and another
physicist across the room is able to detect the wave, that's very nice, and if the
year is 1860, then it's very exciting and they publish a paper and become very
famous and get invited to scientists' parties. But they still don't have anything
that they can use to carry a news bulletin, a weather forecast, or rap music from
one place to another, not even across the laboratory.
In order to carry any information on the radio wave, it has to be changed in some
way from time to time, according to some kind of pattern that the people on both
ends have worked out.
The easiest way to do that is to turn the wave on and off, according to some
system of patterns. Make a different pattern for each letter of the alphabet,
and then you can spell out any message you want to send from one end to
the other. That's exactly how information was sent over radio waves, at the
beginning and for quite a long time. The most widely used set of patterns for
letters and numbers was the Morse Code. To use it, the radio waves only had
to be switched on and off. Anybody anywhere who could detect the wave just
clearly enough to be able to tell when it's on and when it's off, and knew the
code, could "copy" the message.
Later on, with the development of more advanced electronic components,
methods were developed that could change the amplitude or frequency of the
radio waves, very rapidly, and those changes could be used on the receiving
end to construct sounds, that could almost duplicate sounds used to cause
the changes at the sending end. At that point, you then had a way to send
a speech by the president, a weather report, the sound of a live orchestra,
a church sermon, or the voice of a professional singer, over great distances.
Anyway, we're wandering far from a short answer to the question.
"Modulation" is the process of changing the pure radio wave in some way,
for the purpose of causing it to carry information.
Wiki User
∙ 12y agoModulation is applied to a carrier.
If the carrier wasn't modulated it wouldn't carry any information other than that the transmitter was working. Not very useful.
It is the modulation which contains the "information" which we want to send.
Wiki User
∙ 13y agoSome characteristic of the radio wave is changed corresponding to the information,
according to a pattern that has been agreed between the sender and receiver.
The receiver then observes the changes, interprets them according to the agreed
pattern, and reconstructs the information.
Simplest example: Radio wave is turned on and off, representing each letter, digit,
and punctuation with a unique pattern of long and short 'on' and 'off' periods that
the sender and receiver have agreed on. The receiver monitors the patterns of
on/off and short/long, compares them to the agreed patterns, and reconstructs
the message out of letters, digits, and punctuation. The most popular and widely-used
set of on/off patterns is called the "Morse Code".
Other widely-used methods of adding information to radio waves consist of varying
the amplitude, frequency, or phase of the waves according to an agreed pattern.
Add your answer:
Earn +20 pts
Why FM is clearer than am?
The abbreviations FM and AM stands for amplitude modulation and frequency modulation. The reason why FM is more clearer than AM is because FM has a better signal-to-noise ratio than AM does.
Can you make a left turn onto a one way street at a red light from two way traffic street?
If you are making a left turn onto a one way street and the red signal is a circle not an arrow, the same rules apply as to right hand turns on a red light (it is legal after a full stop and checking for oncoming traffic). However if the signal is a red arrow, you cannot turn against it.
What do AM waves and FM waves have in common?
Both are radio waves, meaning that they are electromagnetic radiation (light) with a wavelength longer than a metre. AM waves have a frequency of 520,000 Hz to 1,620,000 Hz (wavelengths of 580 metres to 185 metres) while FM waves have a frequency of 87,500,000 Hz to 108,000,000 Hz (3.4 metres to 2.8 metres). The signal is encoded onto AM waves by varying the amplitude (intensity) and onto FM waves by varying the frequency.
When was Something to Hold Onto created?
Something to Hold Onto was created in 2002.
Can you download music onto your x-mini speaker?
can you download music onto your mini speaker
How does the FSK modulator circuit work?
The FSK (Frequency Shift Keying) modulator circuit works by shifting the carrier, a sine wave of a given frequency, to another frequency back and forth as the input signal changes. On the receiving end, the demodulator works by detecting one or both of the frequencies, often with a band-pass filter, regenerating the input signal. You can also use a signal processor to convert the carrier from time domain to frequency domain with a fourier transform, and then pick off the signal that way.) The FSK method of modulating/demodulation is typically limited to low frequency signal rates, such as 300 bits per second. You can also modulate multiple input signals onto one carrier, but the workable signal rate of each goes down. (In one signalling example, six analog inputs were used to duty cycle modulate six 10 hertz pulse trains, which were then FSK modulated onto one carrier. The receiving end had six band-pass filters, and six converters back to the analog domain.) If you are going to modulate more than one signal, you need to pick the frequencies carefully, so that their harmonic spectra do not intersect, otherwise you could get cross-talk if there is distortion in the carrier.)
Why analog data have to be modulated onto an analog signal?
For transmission through a radiowave.
What is difference between modulated wave and carrier wave?
Carrier Wave: A carrier wave is a high-frequency electromagnetic wave that is used as the "carrier" or the base signal in a modulation process. It is typically a pure sine wave with a constant frequency and amplitude. The carrier wave by itself does not carry any information; it serves as a vehicle to carry the information from one location to another. In AM and FM radio broadcasting, the carrier wave is the primary signal transmitted by the radio station. Modulated Wave: A modulated wave is the result of combining the carrier wave with an information signal, such as an audio signal or data. Modulation is the process of varying the characteristics of the carrier wave (either its amplitude or frequency) in accordance with the information signal. There are two common types of modulation: Amplitude Modulation (AM) and Frequency Modulation (FM). In AM, the amplitude of the carrier wave is varied in proportion to the amplitude of the information signal. This variation encodes the information onto the carrier wave. In FM, the frequency of the carrier wave is varied in proportion to the amplitude of the information signal. This variation encodes the information onto the carrier wave. The modulated wave contains the information that needs to be transmitted, and it can be demodulated at the receiving end to retrieve the original information.
What does the term keying mean in PSK?
Grab a seat and we'll kick it about PSK. PSK is phase shift keying. It's a modulation scheme, a way to put digital information onto a carrier wave. Let's do a quickie review and then go right to the answer. Ready? Let's jump. Let's say we need to send a digital signal. Our signal, the digital string, is just a series of "on's" and "off's" that isn't much different from something like, say, Morse code. The telegraph code could be looked at as a binary code. It's just short and long pulses, not unlike our binary on's and off's in the digital domain. So how do we get that information onto a carrier wave? One way is to shift the phase of the carrier signal to modulate it, to add our signal to it. Let's look at the carrier wave. We have a carrier humming along at (probably) some microwave frequency. If we want to send an 'on' bit, we slow down the carrier just a tad, and for a tiny interval of time. If we want to send an 'off' bit, we speed the carrier up just a tad for a tiny interval of time. The slowing down or speeding up of the carrier in PSK is the keying. Wouldn't it be nice to know what effect this has on the other end of the transmission? Let's look. On the receiving end, we generate the original carrier frequency (our "beat" frequency), and then we "beat it against" the incoming signal. (Our generated signal in the receiver is held tightly "dead on" the carrier frequency.) When we beat the two signals together, if they are the same frequency, there is no "differential" signal generated. If the transmitter is slowing the carrier down a tad or speeding it up a tad, our detectors in the receiver will "see" the difference between the incoming signal and the signal that the receiver is beating against it. The differences are logged as on's and off's by the receiver, and the digital data is then reassembled to recreate the original pulse string. Piece of cake. Oh, and got a link for ya.
What is satellite switched time division multiple access?
Time division multiple access (TDMA) is a modulation scheme used to impress a digital signal onto a carrier and allow it to be effectively demodulated on the receiving end. Whether it's a cell phone, satellite or whatever, some kind of "agreement" must be worked out in advance to allow devices to connect. TDMA is one kind of way to modulate the signals. Think of AM and FM radio. One cannot receive the other, and agreement must be made in advance between the transmitter and receiver(s) as to how the information being passed on is going to be put onto the carrier signal. And, as stated, TDMA is one way this modulation if "formulated" so information can be put on a carrier and taken off at a user's end.
What is the difference between digital and analog electromagnetic signals?
There is no modulation of a Digital Circuit.Modulation is placing information onto an analog circuit to transport thatinformation to a distant location to be decoded/demodulated.Having said that, you can modulate a digital signal in dozens of ways,(Modem) and you can also modulate an analog signal dozens of ways(AM Radio Station, CB Radio, Walkie Talkie, FM Rock Station).NoteWhat this question may really be asking about is something like:"What are the differences between using an analog signal and a digital signal when you want to encode some information for transmission?"so that has now been posted as a separate question.
What is a demodulator?
The process of separating the original information or SIGNAL from the MODULATED CARRIER. In the case of AMPLITUDE or FREQUENCY MODULATION it involves a device, called a demodulator or detector, which produces a signal corresponding to the instantaneous changes in amplitude or frequency, respectively. This signal corresponds to the original modulating signal
Differentiate FM signal from AM signal?
FM = Frequency Modulation; AM = Amplitude Modulation; each being a technique by which the speech signal is imprinted onto the carrier signal (the one to which you tune the radio). FM is a higher frequency than AM. FM also only uses the 2.7hz upper side band of the frequency while AM utilizes the entire 6hz both the LSB, USB and the .6hz carrier wave. That allows AM to travel farther than a FM signal.
Which happen first the modulation or the multiplexing?
A terminal may transmit several application, at a time. All such data of that terminal is multiplexed, and this multiplexed signal is modulated onto a carrier.
What is Modulation and what is the aim of modulation?
Modulation is any of several means of encoding an information carrying signal onto a carrier of fixed frequency. The purpose is to allow the information to be transported long distances.
What is the difference between FM transmitters?
Fro transmitting FM signals from one point to another,one need to have a full system that transforms your signal. The FM transmitter and FM modulator are two parts of this system and they are both necessary in making the system function as desired. The transmitter is the part that dissipates the FM signal into the air so that it can be received by antennas somewhere else. The FM modulator, on the other hand, is responsible for piggybacking the signal onto the carrier signal. Refer american-writers.org for more information.
What is the difference between baseband coaxial cable and broadband coaxial cable?
Iam pretty sure that baseband coax was 50 ohm and was used for networking computer, were broadband coax is 75 ohm and used in the cable tv industry. A baseband signal is the original signal before it is modulated onto a carrier, mulitplexed or mixed. A broadband signal contains many channels which have been modulated or multiplexed onto a common carrier. The significant difference is the bandwidth of each. The impedance of the cable which carries either of them is totally irrelevant to the definition.
