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Radio- kind wireless communications, in which a carrier signal using radio waves, freely distributed in space.
How it works
The transfer is as follows: at the transmitting side is formed of radio waves (signal) with the required frequency and power. Then the transmitted signal modulates a high frequency oscillation (carrier). The resulting modulated signal emitted by the antenna in space. At the receiving side of radio waves induce a modulated signal in the antenna, then it is filtered and demodulated. After demodulation signal is obtained, with some (possibly valid) differences with the signal, which we passed on the transmitter.
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Frequency Bands
Depending on the range of radio waves have their own characteristics and laws of propagation:
• IR strongly absorbed in the ionosphere, the main significance Surface waves, which are distributed, skirting the land. Their intensity with distance from the transmitter is reduced relatively quickly.
• S strongly absorbed in the ionosphere during the day, and the area of surface wave action is determined, in the evening is well reflected from the ionosphere and the District of is determined by the reflected wave.
• KV distributed exclusively by the reflection of the ionosphere, so there is a transmitter around the so-called. Area radio silence. Happy is better distributed over the short-wave (30 MHz), at night - a long (3 MHz). Short waves can propagate over long distances at low power transmitter.
• VHF extend rectilinearly and usually do not affect the ionosphere. It is easy to bend around obstacles and have a high penetrating power.
• HF does not bend around obstacles, are distributed in line of sight. Used in WiFi, cellular, etc.
• EHF not bend around obstacles that affect the majority of the obstacles are distributed in line of sight. Used for satellite communications.
• Hyper-frequencies does not bend around obstacles, like the reflected light propagating in the line of sight. Restricted.
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Origins and early development
Personality original inventor of radio, at the time called wireless telegraphy, is contentious. The key invention in the beginning of "wireless data transfer using the entire frequency spectrum", known as a transmitter with a spark arrester, is attributed to Nikola Tesla, Guglielmo Marconi and Alexander Popov.
In the history of radio and the development of "wireless telegraphy", there are several candidates for the invention of radio. Tesla developed a device for generating sound signals, publicly demonstrated the principles of radio and the first radio signals transmitted over long distances. Marconi equip the ships life-saving wireless communications, has created the first transatlantic radio service.
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Using a variety of patents, was founded a company called British Marconi ", which establishes the radio link between the shore stations and ships at sea. This company, together with its subsidiary branch in America took a stranglehold on the ships to expand its business by radio communication. The company has acted in this way until 1983 through the U.S. company ATT, owning all of its internal equipment, and refusing to communicate with ships equipped with Marconi apparatus not. Many inventions gradually improved the quality of the radio, and amateurs experimented with the use of radio - both were planted the first seeds of broadcasting. At the turn of the century, Adolf Slaby and Georg von Arco developed a wireless communication system Slaby-Arco (later introduced in Telefunken).
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The development of radio in the XXI century
Telegraphy by radio does not disappear, however, the degree of automation increases. From the land lines of the 1930's to the teletype automated coding, then these funds have been adapted to pulse-code dialing, and automatic routing, and finally appeared telex. For thirty years, Telex is the cheapest means of distance communication, as well as 25 channels telex occupy the same bandwidth as one voice channel. For business and government is important that the telex could send the signed documents.
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Telex systems were adapted to short range by using only one side of the band to send tone signals. The most modern pure telex standard CCITT R.44 includes error detection and retransmission at the level of symbols, as well as automated encoding and routing. For many years, telex-on-radio (TOR) is the only reliable way to achieve connection with some third-world countries. Telex is still reliable, although some cheaper form of e-mail vytesnyut it. Many national telecommunications companies have traditionally used pure telex networks for their governments, and many of these networks operate on short waves.
Internet radio or web radio - a group of streaming audio technology via the Internet. No radio or radio in these technologies is not required.
Now you know a lot more!
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