Allocation of Frequencies in the Radio

Alkali metals see entries for Lithium, Sodium, etc. Allocation of Frequencies in the Radio Spectrum, 15-50 to 51... 

Microwaves are electromagnetic radiation placed between infrared radiation and radio frequencies, with wavelengths of 1 mm to 1 m, which corresponds to the frequencies of 300 GHz to 300 MHz, respectively. The extensive application of microwaves in the field of telecommunications means that only specially assigned frequencies are allowed to be allocated for industrial, scientific or medical applications (e.g., most of wavelength of the range between 1 and 25 cm is used for mobile phones, radar and radio-line transmissions). Currently, in order not to cause interference with telecommunication devices, household and industrial microwave ovens (applicators) are operated at either 12.2 cm (2.45 GHz) or 32.7 cm (915 MHz). However, some other frequencies are also available for heating [1]. Most common domestic microwave ovens utilize the frequency of 2.45 GHz, and this may be a reason that all commercially available microwave reactors for chemical use operate at the same frequency. 

In 1979, the ISM frequency allocations were revised as a result of the World Administrative Radio Conference (WARC) (16). A considerable effort was made to increase the number and worldwide uniformity of ISM frequency allocations. Most of those proposals were rejected. The resulting allocations are Hsted in Table 1. 

The remaining ISM allocations above 433.92 MHz are not harmonically related. This is unfortunate in terms of the problem of minimizing radio-frequency interference (REI), except for the harmonic relation in the millimeter wave range. 

In the United States the National Telecommunications and Infonnation Administration (NTIA) has responsibility for assigning each portion of the radio spectrum (9 kHz to 300 GHz) for different uses. These assignments must be compatible with the rules of the International T elecommunications Union (ITU), to which the United States is bound by treaty. The current assignments are given in a wall chart (Reference 1) and may also be found on the NTIA web site (Reference 2). The list below summarizes the broad features of the spectrum allocation, with particular attention to those sections of scientific interest. The references should be consulted for details of the allocations in the frequency bands listed here, which in some cases are quite complex. 

Transmitter That portion of a radar system allocated the responsibility for generating the radio frequency (RF) signal that is launched in the desired direction. 

Certain bands of the EMR spectrum have been allocated specific applications. The various radio frequency bands and their frequency ranges are shown in Table 2.7. 

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