1:why do FM radio stations have good clarity inspite of having very close frequency?

Question

precise answers,websites needed

Answer 1

The method of modulation.

For Amplitude Modulation (AM) the carrier amplitude is modulated by the amplitude of the the audio signal. This is susceptible to amplitude noise hits.

For Frequency Modulation (FM) the carrier frequency is modulated by the amplitude of the audio signal. A voltage controlled oscillator (VCO). Because the information is carried based on the frequency of the signal rather than the amplitude of the signal, it is less susceptible to amplitude noise hits. So as the lyrics of the old Steely Dan song "No static at all, FM."

Answer 2

If, by clarity, you are referring to the perceived audio quality of what you hear from your radio, then the "clarity" of a signal doesn't really have anything to do with neighboring frequencies.

The simplest answer is because FM signals (using VHF, or "very high frequencies) have a high bandwidth. In other words, it can carry a lot of information on one frequency.

In the case of FM radio, that information is the audio you hear. Think of it as you would computer graphics- higher resolution and more colors equal better detail.

In the broadcast world, this means "high fidelity"

If, on the other hand, when you say clarity, you are referring to reception- the quality of reception depends upon the strength of the signal (not the frequency) and the quality of your receiving device.

I do not list websites because I don't need to reference them. I'm an audio engineer.

Answer 3

FM Radio stations are 100kHz apart whereas AM Radio stations are 10kHz apart. So your basic premise is not correct. FM Radio has a lot more bandwidth per station, which helps the clarity. Also the Frequency Modulation (FM) provides a noise reduction over Amplitude Modulation (AM).

Answer 4

the_dude is warm. Any radio channel is really a single center frequency, but also a spread of frequencies around that center frequency.

So yes, FM channels have a much greater spread of frequencies (higher RF bandwidth) about that center frequency compared to AM channels. This makes the sound more "Hi-Fi" for FM compared to AM. But the higher bandwidth also improves the RF reception quality. This is separate from signal strength issues.

Finally, the modulation method for FM is much better than AM in rejecting spurious signals such as auto ignition systems, lightning & related weather effects.

Answer 5

Good answer by rscanner. Just a minor correction: FM stations are actually 200 kHz apart (101.1, 101.3, 101.5 etc. in MHz. There are not stations at 101.2, 101.4, etc.)

At any rate, that is more than sufficient to cover the 20 kHz bandwidth needed for a normal human range of hearing.

Answer 6

http://www.pbs.org/wgbh/aso/tryit/radio/radiorelayer.html