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The radio spectrum is the part of the electromagnetic spectrum from 1 Hz to 3000 GHz (3 THz) allocated to some 40 Radiocommunication services in line to the Radio Regulations (RR) of the International Telecommunication Union (ITU).〔International Telecommunication Union´s Radio Regulations, Edition of 2012.〕 The transmission, emission and/or reception of radio waves for specific telecommunication purposes of radio waves is strictly regulated by the national administration.〔ITU Radio Regulations – Article 1, Definitions of Radio Services, Article 1.2 Administration: Any governmental department or service responsible for discharging the obligations undertaken in the Constitution of the International Telecommunication Union, in the Convention of the International Telecommunication Union and in the Administrative Regulations (CS 1002).〕 Different parts of the radio spectrum are allocated for different radio transmission technologies and applications. In some cases, parts of the radio spectrum is sold or licensed to operators of private radio transmission services (for example, cellular telephone operators or broadcast television stations). Ranges of allocated frequencies are often referred to by their provisioned use (for example, cellular spectrum or television spectrum). ==By frequency== A band is a small section of the spectrum of radio communication frequencies, in which channels are usually used or set aside for the same purpose. Above 300 GHz, the absorption of electromagnetic radiation by Earth's atmosphere is so great that the atmosphere is effectively opaque, until it becomes transparent again in the near-infrared and optical window frequency ranges. To prevent interference and allow for efficient use of the radio spectrum, similar services are allocated in bands. For example, broadcasting, mobile radio, or navigation devices, will be allocated in non-overlapping ranges of frequencies. Each of these bands has a basic bandplan which dictates how it is to be used and shared, to avoid interference and to set protocol for the compatibility of transmitters and receivers. See detail of bands:http://www.ntia.doc.gov/files/ntia/Spectrum_Use_Summary_Master-06212010.pdf As a matter of convention, bands are divided at wavelengths of 10n metres, or frequencies of 3×10n hertz. For example, 30 MHz or 10 m divides shortwave (lower and longer) from VHF (shorter and higher). These are the parts of the radio spectrum, and not its frequency allocation. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Radio spectrum」の詳細全文を読む スポンサード リンク
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