14 Frequency ranges in use
Theoretically all radio frequency signals above dc will radiate electromagnetic energy and thus propagate through space. However, for those frequencies below about 15 kHz the radiation is insignificant. This figure should not be confused with the higher limit of the audibility of sound waves by the human ear. Radio and sound waves propagate via completely different phenomena. Typically then, the part of the electromagnetic spectrum that is suitable for radio communications lies in the range 15 kHz to 300 GHz, although current applications above about 30 GHz are very limited. The ranges and nomenclature of the various sub-bands in use are shown in Table 14.1.
The frequency ranges used for microwave communications are ...
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