what is AM and FM radio?


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AM and FM radio represent what?

In general on the radio or tape recorder collection has AM and FM bands, I believe we are already familiar with these two bands are used for you to listen to the domestic broadcast the radio SW, then in addition to the domestic shortwave radio you can also listen to radio programs in the world. In order to further understanding of the use of radio, the following for a brief description of AM, FM, SW, LW.

In fact, the AM and FM refers to the radio science on the two kinds of different modulation methods.
1. AM: Amplitude Modulation called amplitude modulation
The amplitude modulation is a modulation signal to control the amplitude of the high-frequency sinusoidal carrier, so the process of changes in the law by the modulating signal. The frequency spectrum of the AM signal by the carrier frequency component and on the the next two sidebands composition (usually called the hatched portion in the spectrum for the upper sideband, the hatched portion is lower sideband). The spectrum of the upper sideband and the same structure as the original modulation signal spectrum, the lower band is the mirror image of the upper sideband. Obviously, both the upper sideband or a lower sideband contains the complete information of the original modulation signal. Therefore, AM signals are double sideband signals with carrier, its bandwidth twice the signal bandwidth.
Generally medium-wave broadcasting using amplitude modulation (AM) (MW: Medium Wave), unknowingly, MW and AM draw an equal sign. Actually MW of only one of many AM modulation method a broadcast, as in HF (3-30MHz) in the international shortwave broadcast using a modulation mode is also AM, or even a higher frequency than the FM broadcasting aviation navigation and communication (116 – AM the way, 136MHz) is just our daily said the AM band is the medium wave the broadcast (MW).

 

2. FM: Frequency Modulation called FM.
We are used to with FM refers the general FM radio (76-108MHz), the fact is also a FM modulation, even in the short wavelength range between 27-30MHz, as amateur radio, space, satellite communications applications band , frequency modulation (FM).

What is SW? In fact, you can say that to shortwave a simple call, the correct statement should be a high-frequency (HF: High Frequency) is more appropriate.
Shortwave how to name it? In the wavelength, the wave (MW) range of between 200-600 meters (yards), and the wavelength of the HF is between 10 to 100 m (meters), compared with the above-described wavelength, HF of wavelength is short indeed some put HF called short-wave (SW: short Wave).
Similarly, the ratio between this period of the spectrum in the medium wave MW lower frequency 150KHz-284KHz is as broadcast with the wavelength, called the long-wave (LW: Long Wave), which is about 1000 to 2000 m (male feet), and MW 200-600 meters relative comparison is obviously “long”, so put this spectrum of broadcast called longwave (LW: Long Wave).
In fact, regardless of the long-wave (LW), medium wave (MW) or short-wave (SW) and are based on the AM modulation. General admission (recorded) sound machine in terms of the FM, MW and LW band to provide you listen to domestic broadcasting, SW, mainly for you to listen to the domestic / international long-distance broadcasting.

 


Sample/Wholesale
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1 pcs sample
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pcs
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