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F.M has low noise in received signal than A.M, the reason is being that Noise signal is amplitude mdulated and will be received by the A.M. receiver and will be rejected by Frequency modulation (F.M) receiver. Because F.M is designed to receive frequency modulated signals.
In the course of communication through electromagnetic waves (em) the message waves are usually not able to traverse long distances due to their large wavelength and hence less energy. So for long distance communication, the message wave is superposed on some other high frequency carrier wave which is known as modulation. That can be done in three ways
- by changing the amplitude of carrier wave(am)
- by changing the frequency of carrier wave(FM)
- by altering the phase of carrier wave(pm)
so as the amplitude and energy of am wave can change due to atmospheric disturbances am is distorted but no disturbances can alter the frequency and hence FM is clearer
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Also, Radio waves are a form of light. When a radio wave is amplitude modulated, it varies the "brightness" of the signal. and a "brighter" source of radio waves, like a lightning bolt or the noise from TVs or Computer equipment is "seen" by the radio easier than the actual radio signal, blocking it out.
FM Radio is like varying the "color" of the radio wave, so if you have a brighter source, you can still see the color of the source (signal), and therefore noise and static.
FM Radio is subject to being reflected in an event called multipath, in which the primary radio signal is reflected by hills and tall buildings, and a secondary signal is received and this causes the ghosting you see on a TV screen or that swishing that you hear on FM in a big city, so FM is still susceptible to noise and static, though not as much as AM.
AM and FM radio waves propagate differently because of their signal strength characteristics. The length of an AM wave allows it to refract against the Earth's ionosphere (a layer of charged particles in the atmosphere) and redirect over the horizon toward a geographical location that could be hundreds of miles away. FM waves in contrast are "line of sight"; the point of transmission must have an unobstructed path toward the receiver. The higher frequency and smaller wavelength of FM signals means that they will go through the ionosphere (and into space) instead of refracting as an AM signal would.
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Why Fm is more immune to noise than AM?
b/c information lies in frequency... while in AM information lies in amplitude and noise effects the amplitude more as compare to frequency....... there for.....
Why FM is more 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.
What is difference between amplitude modulation and frequency modulation with respect to signal to noise ratio?
In FM noise is low as compared to AM. The AM signal covers more distance than FM signal that's why it gets more distorted.How ever the information in AM signal does not lose but the noise effects it more than that of FM signal,so we get signal with more noise than that of FM signal For FM Carson's rule Main article: Carson bandwidth rule A rule of thumb, Carson's rule states that nearly all (~98%) of the power of a frequency-modulated signal lies within a bandwidth of where , as defined above, is the peak deviation of the instantaneous frequency from the center carrier frequency . Noise quieting The noise power decreases as the signal power increases; therefore the SNR goes up significantly. Thanks, By tauseef ahmed
What is the difference between FM and AM?
AM and FM - Difference AM stands for amplitude modulation. It is the older technology for broadcast radio. In an AM signal, the carrier frequency is fixed and the information (audio or other signal) is transmitted by varying the magnitude of the carrier wave. FM stands for frequency modulation. In an FM signal, the magnitude of the carrier wave is fixed and the information is transmitted by varying the frequency of the carrier. An FM receiver can produce a better signal-to-noise ratio, since lightning and other electrostatic noises in the atmosphere can be mistaken for changes in amplitude of an AM signal, but do not resemble the changes in frequency in an FM signal. This led to FM being used increasingly for music broadcasts, where noise was particularly bothersome. As it turns out, AM broadcast stations were also allocated limited bandwidth, which restricted their ability to transmit high-fidelity audio. FM broadcast frequencies were not so restricted. That meant that FM also had better audio bandwidth as well as better signal-to-noise ratio. However, that was a result of the technical decisions by the FCC (and its equivalent in other countries), not an inherent difference between AM and FM technology. There are of course, additional modulation systems for each type of carrier, but that largely depends on the application. Television (NTSC) uses both AM (picture) and FM (sound). HDTV uses digital modulation for both picture and sound.
Why FM is good than am in communication?
The FM signal is more amune to static in the atmosphere than AM signals.
What is noise triangle and effects of noise on carrier?
Noise triangle is a triangular noise distribution for FM.Noise triangle is the study of effect of noise on the carrier signal of the FM wave. for more details contact -Ameya Muley (amymuley@rediffmail.com)
Why is FM superior immunity to noise?
FM systems are far better at rejecting noise than AM systems. Noise generally is spread uniformly across the spectrum (the so-called white noise, meaning wide spectrum). The amplitude of the noise varies randomly at these frequencies. The change in amplitude can actually modulate the signal and be picked up in the AM system. As a result, AM systems are very sensitive to random noise. An example might be ignition system noise in your car. Special filters need to be installed to keep the interference out of your car radio. FM systems are inherently immune to random noise. In order for the noise to interfere, it would have to modulate the frequency somehow. But the noise is distributed uniformly in frequency and varies mostly in amplitude. As a result, there is virtually no interference picked up in the FM receiver. FM is sometimes called "static free, " referring to its superior immunity to random noise.
What is FM threshold effect?
An important aspect of analogue FM satellite systems is FM threshold effect. In FM systems where the signal level is well above noise received carrier-to-noise ratio and demodulated signal-to-noise ratio are related by: The expression however does not apply when the carrier-to-noise ratio decreases below a certain point. Below this critical point the signal-to-noise ratio decreases significantly. This is known as the FM threshold effect (FM threshold is usually defined as the carrier-to-noise ratio at which the demodulated signal-to-noise ratio fall 1 dB below the linear relationship given in Eqn 9. It generally is considered to occur at about 10 dB).
Why FM is mostly preferred to AM in telecommunication?
Nature creates AM noise (static) so FM is clearer
What type of radio receiver do not respond to static interference?
FM radio is inherently less sensitive to natural noise ... not immunebut significantly less sensitive ... than AM radio is.
What is noise triangle?
Noise triangle is a triangular noise distribution for FM.Noise triangle is the study of effect of noise on the carrier signal of the FM wave.
What is pre-emphasis and de-emphasis in FM?
In FM, the effect of noise is more on higher frequencies when compared with low frequencies. Therefore in order to have high signal-to-noise ratio(low noise), the high frequencies are amplified at the transmitter side and for compensation deemphasis(decreasing the amplitude of those boosted frequencies ) is done at receiver.
