Why FM is clearer than am?

Answer 1

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.

Answer 2

The main advantages of FM over AM are: # Lesser distortion. Frequency modulated wave is less susceptible to intereferences from buildings, traffic etc which provides improved signal to noise ratio (about 25dB) w.r.t. to man made interference. # Waves at higher frequencies can carry more data than the waves at low frequency. # Smaller geographical interference between neighboring stations. # Less radiated power. # Well defined service areas for given transmitter power. Disadvantages of FM: # Since attenuation is directly proportional to frequency, so FM suffers more attenuation tham AM signal. # FM signals propagate as line-of-sight phenomenon, so if there is a large hill between transmitter and receiver, the receiver will not receive any signal. AM signals, on the other hand, are at low frequencies which are reflected back by ionospehere and thus, using sky-wave-propagation phenomenon, can travel farther distances. FM waves penetrate ionosphere and are not refracted back. # Much more Bandwidth (as much as 20 times as much). # More complicated receiver and transmitter.

Answer 3

The difference is how the "information" rides on the carrier frequency. And the names give it away. In AM or Amplitude Modulation, the information is added to the amplitude of the carrier signal. When your receiver receives the signal, it does an analog sample of the wave to determine it's average strength, then demodulates the differences in the amplitude to pull out the original information. This is the worst and most inaccurate way of demodulation, for the signal strength is continuously changing, with the analog demodulator always working "behind the times". This is why it took so many years for the occurance of AM Stereo. It's hard enough to accurately pull one stream of info out of the carrier wave. Try pulling two distinct signals out of one carrier wave that is Amplitude modulated. How in the world do you do that??? (But they do have AM stereo now, yet not very popular) The reason it came first, is it is very easy to mix amplitudes, and no complicated circuitry was required in the old days to pull in the correct carrier wave. They couldn't do frequency modulation at first cause the government wouldn't let commercial businesses transmit on high enough frequencies to pull out the original information. Also since AM carrier waves have relatively low frequencies, they can travel quite a distance.

In Frequency Modulation, the information is added to the frequency of the carrier wave. The amplitude of the incoming signal is a mute point as long as it is strong enough where your receiver can lock onto the carrier wave. Carrier frequencies in high ranges were released for commercial use, so they could transmit in the MegaHertz range. Since all information needed in the hearing range is commonly in the 20 to 20KiloHertz range, it was easy to pull the signal in. The information didn't cause enough of a difference in the signal to cause the tuner to filter it out. And since the original carrier frequency is known, and locked in, it was extremely easy to pull out the original information. In fact, you could add 6 or 8 different information signals if you wanted to. Complex, but achievable. Since the demodulation is so accurate, this gives it better clarity, and the ability to modulate 2 separate signals for stereo. However, since the carrier frequency is so high, it bounces off obstacles instead of going through them, thus reducing range.

Answer 4

It really does just depend on the wavelength of the frequency you are transmitting on and not so much the "modulation" as such (AM or FM).

For example, 20mhz at AM will react the same as 20mhz on FM (because the wavelength is the same length). Both AM and FM use the same electromagnetic spectrum (as there is only one spectrum) and therefore if they are the same wavelength, they will be "refracted" (reflected) on the ionosphere the exactly the same way.

Saying this, AM may appear to travel slightly further because; A) it can use slightly less bandwidth than FM (making it travel further) and B) because to decode FM take a slightly stronger signal than AM to hear audible sounds.

AM, in some countries, may also appear to travel further because the frequency allocation is lower down the spectrum than FM. The higher up you go in the spectrum, the more you rely on line-of-sight.

Answer 5

'AM' is the process of encoding information on a radio carrier in the form of changes
in its amplitude. The AM receiver looks for changes in amplitude, and uses those to
reconstruct the information.

'FM' is the process of encoding information on a radio carrier in the form of changes
in its frequency. The FM receiver looks for changes in frequency, and uses those to
reconstruct the information.

Virtually all natural sources of noise have amplitudes that change and frequencies that don't.

Answer 6

Actually, AM is better than FM. AM can cover the world, and is the best form of communication. FM is completely worthless except for the fact that it's better sounding.