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The history of the development of radio, to a large extent, is the people of each band research, the use of history. The first application is a long band, because the long wave in the surface of the induced current is small, radio energy loss is small, and can bypass the obstacles. But the long wave of antenna equipment is huge, expensive, communication capacity is small, which prompted people to seek new communication band. In the 1920s, amateur radio enthusiasts found that shortwaves could travel far away. In 1931 the ionospheric theory appeared, and the ionosphere was like the mirror of Hertz. It is most suitable for reflective shortwave. Shortwave radio is both economical and lightweight, it has been widely used in telecommunications and broadcasting. However, the ionosphere is affected by weather, solar activity and human activities, so that communication quality and reliability decline, in addition to short-band capacity can not meet the growing needs. Short-band for the 3MHz ~ 30MHz, according to each short-wave station accounted for 4KHz band calculation, can only accommodate thousands of radio stations, each country can only share a very limited number of radio stations, television (8MHz) even more crowded. Since the 1940s, the world has developed microwave technology. The microwave is close to the optical frequency, which travels along the line and can not be reflected through the ionosphere, so the microwave needs to be reflected by the relay station or the communication satellite and propagated to the intended distance.
The main purpose
The earliest use of radio in the sailing, the use of Morse telegraph in the ship and land transfer information. Now, radio has a variety of applications, including wireless data networks, a variety of mobile communications and radio and so on.
The radio waves contain a rapidly vibrating magnetic field. The velocity of the vibration is the frequency of the wave, in Hz (Hz). 1 Hz is equal to vibrating every second. One kilohertz (kHz) is equal to 1000 Hz. Different frequency bands are used to transmit a variety of different information.
In 1983, the United States of America Columbia space shuttle implementation of the STS-09 mission, SAREX group (Shuttle / SpaceAmateurRadioExperimentteam) contributed to W5LFL / Owen Garrett (Owen Galriott) became the first amateur radio astronaut in space. Owen was using a Motorola2 meter FM radio and an antenna mounted on the window. "Here is the W5LFL call on the Columbia space shuttle ...", Owen's spare time in the STS-09 space shuttle mission, with hundreds of QSO on Earth's amateur radio, creating amateur radio contact in human aerospace History. Since then, the country's amateur radio group, which the United States SAREX, Germany's SAFEX, Russia's MIREX as the core of the team, continue to develop in the United States space shuttle, Russia's peaceful space station on the amateur radio communications equipment.
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