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Ultrashort wave communication

Time：2020-05-19

Communication that uses radio waves in the 30-300 MHz band to transmit information. Due to the ultrashort waveThe wavelength is between 1 and 10 meters, so it is also called meter wave communication. The entire ultrashort wave band width is 270 MHz, which is 10 times the short wave band width. Because of the wide frequency band, it is widely used to transmit television, FM radio, radar, navigation, mobile communications and other services.

Ultrashort waves are very different from shortwave in transmission characteristics. Due to the high frequency, the emitted skywaves will generally penetrate the ionosphere into space and cannot be reflected back to the ground by the ionosphere, so they mainly rely on space direct wave propagation (only limited diffraction capability). Like light, propagation distance is limited not only by sight distance, but also by mountains and tall buildings. Such as the erection of a few hundred meters high TV tower, the maximum service radius can only reach 150 kilometers. If you want to spread farther, you must rely on interrupt station forwarding.

The wavelength of ultrashort wave is shorter. Therefore, the size of the transmitting and receiving antenna can be small. In short-distance communication, only a small communication device needs to be equipped, so it is widely used in mobile communication. Since the 1980 s, combined with telephone switching technology, mobile stations can form a two-way communication circuit with other mobile stations by dialing through telephone switches, called wireless phones (or mobile phones), and can communicate with the local telephone network to form a convenient and flexible communication network. The smallest mobile radios are handheld and weigh less than 1000 grams. Reporters carry them into the scene for interviews and can keep in touch with the editorial department at any time within tens of kilometers. If you have text fax, image fax or portable computer equipment to write manuscripts, you can interview the manuscript or photo back to the editorial department on the spot.

Keywords： Ultrashort wave communication