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There are several methods for generating FM signals but they all basically involve an oscillator with an electrically adjustable frequency. This type of oscillator uses an input voltage to affect the frequency of its output. For example, when the applied voltage increases, the oscillator output frequency increases and when the applied voltage decreases, the oscillator output frequency decreases as well. If no voltage is applied to the oscillator its output will be a signal at its centre frequency. The amount of frequency variations is deviated around the oscillators' centre frequency.
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How does a high-power FM transmitter work?
Summary: An FM transmitter has an oscillator that generates the carrier RF signal. Frequency modulation takes place at the oscillator stage. The modulated signal is then sent through some filters and then finally amplified by a class C power amplifier, and then delivered to the antenna. An FM transmitter has an oscillator that generates a carrier signal on a desired frequency. But something like a voltage controlled oscillator is used so that the oscillating frequency can be changed by a modulating signal. When there is no modulation, the oscillator runs at it assigned frequency (called a center frequency). The voltage that is controlling the frequency at which it is running is constant. By applying the volage of a modulating signal to that "controlling" voltage, the frequency of the signal can be caused to vary above and below its assigned center frequency in a way that is directly proportional to the modulating signal. It is shifted above and below its assigned center at a rate proportional to the frequency of the modulating signal and at an amount proportional to the amplitude of the modulating signal. This takes up a bit of what is called bandwidth on the electromagnetic spectrum. The modulated FM signal appears as a "group" of frequencies around that center frequency with the sub-group of frequencies about the center being called the upper sideband, and that sub-group below the center being called the lower sideband. Almost all of the power in the generated signal is carried in these sidebands. This RF signal is them amplified by a high power RF amp, and the (now) high-powered FM signal is then sent via a transmission line to an antenna, from where the signal radiates into space. A link is provided to the Wikipedia article on FM modulation. Surf on over and check out the drawings and the little "moving pictures" to get a handle on FM. (No static at all!)
What is indirect method of FM transmitter?
indirect FM transmitter is the transmitter which indirected connectly to the FMINDIRECT FM GENERATIONWhile it is not possible to vary the frequency of a crystal oscillator directly, it is possible to vary its phase. The resulting PM signal can be used to create FM. This is the basis of the Armstrong modulator.The mathematics required to analyze the Armstrong modulator completely are complex, so we will discuss only the basic circuit operation. An audio signal is passed through a preemphasis network and then an integrator, a special network whose output is the time integral of the input signal. The preemphasized integrated signal is used to phase modulate a crystal oscillator. Mathematically, it can be shown that PM using the integral of the audio signal is identical to FM using the audio signal itself. In this way an FM signal is generated.The Armstrong modulator cannot produce much deviation, so combination of multipliers and mixers are used to raise the carrier frequency and the deviation. The multipliers are used to multiply the carrier and the deviation. The mixers are used to decrease the carrier, while keeping the deviation constant so that additional multiplier stages can be used to obtain more deviation. It is worth going through an example:An FM station is authorized to operate at 90.9 MHz, with maximum deviation of 75 KHz. The FM signal is generated with an Armstrong modulator whose output is 500 KHz with a deviation of 15.432 Hz. The modulator output is applied to 3 triplers and a doubler to obtain a frequency of 81 MHz and a deviation of 2.5 KHz. The 81 MHz signal is mixed with a 77.97 MHz signal to produce a 3.03 MHz signal whose deviation is still 2.5 KHz. This signal is fed through a doubler, tripler and quintupler to multiply the carrier to 90.9 MHz and the deviation to 75 KHz.
What is the use of connecting an integrator in delta modulation?
integrator converts the quantised signal to saw tooth signal which then compared with the present signal and error signal is generated,and error signal is quantised and the process continues
Pre-emphasis in FM systems involves?
Amplification of higher frequency component of modulating signal
What is narrow band FM and how a narrow band FM generate?
If the modulation index of FM is kept under 1, then the FM produced is regarded as narrow band FM. Lower the modulation index, lower the no. of significant sidebands are produced (with reference to bessel function). So lower the no. of significant sideband, lowerer will be the bandwidth of the resulting FM prduced. Sometimes, Narrow Band FM is regarded as, when the significant energy in FM occupies the same bandwidth as ordinary AM with the same 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.
Why you convert FM signal to IF frequency?
Mix it with a local oscillator whose frequency is (the IF frequency) away from the frequency of the FM signal you're interested in.
Why are FM tones used in ASSR?
boz there is lesas interferance to the signal as a signal travels...............
How is FM transmitted?
the digital signal is converted to analog signal after using by transmitted antenna
Why is amplitude of demodulated FM signal much less than modulated signal?
because demodulated FM is an audio signal, which the frequency is much smaller that is why it can be transmitted alone. It need carrier which has large frequency. Modulated signal is an audio signal + carrier that is why the amplitude is higher.
Why FM is good than am in communication?
The FM signal is more amune to static in the atmosphere than AM signals.
What signal is generated by a hall sensor?
A: DISTURB signal when the magnetics are in proximity
What determines the amount of deviation of an fm signal?
FM or frequency modulation is a means to vary the frequency withing a set basic frequency and transmit it. FM radio demodulate the frequency extracting the signal that made the frequency shift at the source.
What is the need for limiter in FM receiver?
The limiter clips the top and bottom of the FM signal to remove any AM signal or static that was picked up. This prevents the FM discriminator from seeing those unwanted signals and inadvertently converting them to audio, scrambling the intended audio signal. Simply put, the limiter blocks interference and static making FM reception very clean.
What wave has a shorter wavelength AM or FM?
Generally, the wavelength of an FM signal is shorter than an AM signal. A typical FM broadcast band is 88-108 MHz, while a typical AM broadcast band is 540-1660 KHz, making the FM signal wavelength 100 times shorter.
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 am raido and FM radio?
A: AM radio is an Amplitude Modulation transmission . Meaning it has fix frequency but it is modulated by the signal. FM Frequency Modulation the frequency is modulated by the signal
