The development of remote control lifting bracket principle Radio

Time：2020-12-02 View：

Radio refers to the electromagnetic wave propagating in all free space (including air and vacuum), which is a limited frequency band. The upper frequency is 3THz (terahertz), and the lower frequency is relatively inconsistent, in various RF specifications, the common ones are 3kHz ~ 3THz (stipulated by ITU-International Telecommunication Union),9kHz ~ 3THz,10kHz ~ 3THz.

Development history

 

Discovery of electromagnetic waves
In the 1960 s, Maxwell put forward the theory of electromagnetic field and theoretically speculated the existence of electromagnetic wave. Unfortunately, he died young and lived only 48 years old, which failed to prove the correctness of his speculation by experiments.
In 1887, Hertz, a 29-year-old German, first discovered and verified the existence of electromagnetic waves. Hertz's great discovery not only creates conditions for radio communication, but also determines that electromagnetic waves, like light waves, have properties such as reflection, refraction and polarization, it verifies Maxwell's theoretical speculation that light is an electromagnetic wave.
Hertz found that electromagnetic waves could pass through the wall without hindrance, but they were blocked when they encountered large and thin metal sheet. He also measured the wavelength of electromagnetic wave and calculated the speed of propagation of electronic waves, and found that its propagation speed in vacuum was as fast as that of light. Now we often say that radio waves, infrared rays, visible light, ultraviolet rays, X-rays and gamma rays are all electromagnetic waves.
In order to commemorate the great contribution made by this young scientist to mankind, people use his name to name some concepts of physics and mathematics, such as "Hertz wave", "Hertz", "Vector", "Hertz function", etc., and uses "Hertz" as the unit of frequency.

 

The invention of radio
In 1895, Guglielmo Marchese Marconi (1874-1937), an Italian, successfully conducted the experiment of transmitting signals by radio waves, and went to Britain to apply for a patent the following year. He founded Wireless & Signal Co.,Ltd. in 1897., renamed Marconi's cotton CO.,Ltd.) in 1900, in 1899, radio communication between Britain and France across the Strait of ENGLINE was established. In December 1901, he pulled the antenna with a kite in Canada and successfully received the wireless telegram on the other side of the Atlantic Ocean. The News of the successful experiment made a sensation in the world. Since then, military fortresses and harbor ships of many countries have begun to be equipped with radio-communication equipment, and have played an important role in maintaining contact between ships sailing in the ocean and land, ensuring maritime safety and military communications.

 

Spread of radio technology
On April 1, 23rd, Guangxu (May 2, 1897), the 25th volume of "Time News" published the translation of "Wireless Telegraph", which was the earliest emergence of the word "Wireless Telegraph" in China. Since then, the prelude to the spread of wireless telegrams through periodicals has been opened. The early spread of wireless telegraph technology mainly focused on comprehensive journals, mostly introducing new articles. Then, scientific and technological papers introducing principles appeared, including the latest articles on technology and inventions. With the development of wireless telegraph technology, the content spread in periodicals has also changed, and many legal articles have appeared. Judging from the articles spread in the journals in the late Qing Dynasty, it has formed its own system, which lays a theoretical foundation for the emergence of professional journals and the formation of discipline system in the future.