For a long time, WX communication has played an important role in field exploration, border patrol, earthquake relief and other activities because of its advantages of wide coverage, flexible networking and not limited by geographical environment.However, due to the insufficient number of small terminals, various types of equipment, and the lack of interconnection and interoperability, the rapid mobile communication needs of rescue teams are still not met.Against this background, the WX mobile system came into being. This article will give you a detailed explanation of the origin and development of WX mobile system.First, the WX is going to run.In July 2008, academicians Sun Jiadong and Shen Rongjun jointly wrote a letter **, calling for speeding up the construction of China's own WX mobile communication system.After more than three years of demonstration and design, in 2011, China's first WX mobile communication system - Tiantong No. 1 WX mobile communication system project of...
2018
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![Why is the antenna tower very high?]( "Why is the antenna tower very high?")
If you look at it a little bit, you can see that the antenna towers are all high around you, or you can just put a signal tower on a local high-rise.I never knew why I had to do this before, but I took it for granted.However, after learning the principle of communication recently, the reason why the antenna tower is relatively high can be understood.Under the understanding of sight distance propagationLine-of-sight propagation (LOS propagation) refers to the propagation of space wave between two points that can be directly reached when ultra-short wave and microwave are used for ground communication and broadcasting. Its distance is similar to that of the people on the ground, and generally does not exceed 50km.High-frequency (2MHz ~ 30MHz) electromagnetic waves, known as high-frequency electromagnetic waves, can penetrate the lowest atmospheric ionosphere, but will be reflected back to the ground by the upper ionosphere, the ground will reflect the electromagnetic waves back to the at...
2018
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10
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17
For a long time, WX communication has played an important role in field exploration, border patrol, earthquake relief and other activities because of its advantages of wide coverage, flexible networking and not limited by geographical environment.However, due to the insufficient number of small terminals, various types of equipment, and the lack of interconnection and interoperability, the rapid mobile communication needs of rescue teams are still not met.Against this background, the WX mobile system came into being. This article will give you a detailed explanation of the origin and development of WX mobile system.First, the WX is going to run.In July 2008, academicians Sun Jiadong and Shen Rongjun jointly wrote a letter **, calling for speeding up the construction of China's own WX mobile communication system.After more than three years of demonstration and design, in 2011, China's first WX mobile communication system - Tiantong No. 1 WX mobile communication system project of...
2018
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10
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17
Antenna system is composed of transmitting antenna and receiving antenna. The former is a transmission mode converter that converts the radio frequency current or electromagnetic wave of guided wave mode into the space electromagnetic wave of diffuse wave mode, and the latter is a transmission mode converter of inverse transformation.As the transmitting antenna used in the mode conversion of guided traveling wave to diffusion wave, the receiving antenna I used in the mode conversion of diffusion wave to guided traveling wave is called reciprocity theorem, except that the transmitting antenna's power bearing capacity and voltage bearing capacity are far greater than the receiving antenna's, both of them can be exchanged and the basic characteristic parameters of the antenna remain unchanged. Another important function of the antenna is to concentrate the energy of the electromagnetic wave, that is, to concentrate the energy in the transmitting direction while reducing the energy...
2018
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10
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On April 2, 2018, after accurate calculation and monitoring analysis by the Beijing Space Flight Control Center, Tiangong I re-entered the atmosphere at about 8:15 on the same day, landing in the central South Pacific Ocean, and finally achieved a perfect farewell with its gorgeous posture. On September 29, 2011, at 21:16:03, Jiuquan Satellite Launch Center launched, from this moment on the sky belongs to China's target aircraft and space laboratory. The name "Tiangong" is mainly to cater to the diligent pursuit of unknown space in Chinese traditional mythology. The ancients regarded "Tiangong" as the most sacred place. The main tasks of Tiangong-1 are: completing the space rendezvous and docking mission with Shenzhou-8; guaranteeing the life and work of astronauts during their short-term residence in orbit, ensuring the safety of astronauts; carrying out space applications (including space environment and space physical exploration), space science exp...
2018
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10
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17
![Why is the antenna tower very high?]( "Why is the antenna tower very high?")
If you look at it a little bit, you can see that the antenna towers are all high around you, or you can just put a signal tower on a local high-rise.I never knew why I had to do this before, but I took it for granted.However, after learning the principle of communication recently, the reason why the antenna tower is relatively high can be understood.Under the understanding of sight distance propagationLine-of-sight propagation (LOS propagation) refers to the propagation of space wave between two points that can be directly reached when ultra-short wave and microwave are used for ground communication and broadcasting. Its distance is similar to that of the people on the ground, and generally does not exceed 50km.High-frequency (2MHz ~ 30MHz) electromagnetic waves, known as high-frequency electromagnetic waves, can penetrate the lowest atmospheric ionosphere, but will be reflected back to the ground by the upper ionosphere, the ground will reflect the electromagnetic waves back to the at...
2018
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10
-
17