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What are the factors that accelerate the development of radio broadcasting?

Date:2021/2/24 9:51:18 Hits:



Radio broadcasting technology is developed on the basis of wireless telegraphy and wireless telephone. The invention and application of tubes with various functions accelerated the development of radio broadcasting. Radio broadcasting has undergone three major technological innovations since its invention.





Radio broadcasting uses electromagnetic waves to transmit sound information. The propagation technology is very complicated, but it can be roughly divided into two steps. The first step is to turn voice signals such as language and music into low-frequency electrical signals, which cannot be transmitted. The second step is to turn low-frequency electrical signals into high-frequency electromagnetic waves, which are emitted from the air through an antenna. The process of converting low-frequency electrical signals into high-frequency electromagnetic waves is called modulation. The unmodulated high-frequency electromagnetic wave is called the carrier wave, which can "carry" the low-frequency electric signal with sound information, and the modulated high-frequency electromagnetic wave is called the modulated wave. If the low-frequency electrical signal with sound information is compared to a bicycle, then the high-frequency electromagnetic wave without modulation is like an airplane, and the modulated wave is like an airplane full of bicycles. Each carrier has a certain amplitude and frequency. Electromagnetic wave is a kind of transverse wave, and its amplitude is also called amplitude, which is the distance from the peak or trough to the axis of abscissa. Frequency is also called weekly rate, the number of times the electromagnetic wave vibrates per second, and the unit is "Hertz", or "Hertz" for short. In the radio broadcasting transmission technology, the amplitude of the modulated carrier is called AM broadcasting, and the frequency of the modulated carrier is called FM broadcasting.





The initial radio broadcast transmission technology adopted the amplitude modulation (AM) system, which is a method of modulating the amplitude of the carrier wave in accordance with the changing law of the required transmission signal. A modulator is used to modulate the carrier wave into an amplitude modulated wave. This technology is often used in radio broadcasting and other radio communications. Amplitude modulation is used in long-wave, medium-wave and short-wave broadcasting. Its advantage is that it occupies a narrow frequency band, generally not greater than 20 kHz, so it can accommodate a large number of broadcasting stations in the narrow medium and short-wave frequency bands. Moreover, the AM radio has a simple structure and low cost.





However, the anti-interference performance of AM broadcasting is poor, and the sound is loud when receiving. The physicist Armstrong put forward the theory of frequency modulation (FM) broadcasting for the shortcomings of AM broadcasting. This is a modulation method that changes the instantaneous frequency of the carrier wave according to the changing law of the required transmission signal. The carrier is modulated into a frequency modulated wave with a frequency modulator. FM technology is widely used in radio broadcasting, TV sound and radio communication. In 1933, Armstrong created the first FM radio station, which overcomes the interference of neighboring stations and thunder and lightning, and can keep the sound fidelity extremely high. Compared with AM broadcasting, FM broadcasting has strong anti-interference ability, beautiful sound quality and large coverage area. After the Second World War, FM broadcasting developed rapidly. However, the technology of FM broadcasting is more complicated, the cost of building the station is high, the frequency band occupied is relatively wide, and the FM radio can be used to receive Marconi. This broadcasting technology is generally only used for ultrashort wave transmission.


TV audio also uses FM broadcasting technology, but because the frequency of TV audio is different from that of broadcast, FM radio cannot receive TV audio. 



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