Satellite broadcasts are transmitted within or just slightly below the microwave frequency band for a number of reasons. First, higher frequency signals have the potential for relaying larger quantities of information because, as the frequency increases, any given bandwidth becomes a smaller fraction of the carrier frequency. Second, signals transmitted at microwave frequencies can be aim into a highly directional beam towards an extremely small target in space. Third, microwave transmissions to satellites or between earth-based, line-of-sight relay stations are not as susceptible to noise from atmospheric disturbances as are lower frequency transmissions. Fourth, microwaves are able to pass through the upper atmosphere into outer space. Below frequencies of approximately 30 MHz, a radio wave will be reflected back from the ionosphere layer in the atmosphere towards earth. Fifth, the microwave region within the electromagnetic spectrum was a virgin territory during the late 1950s and 60s when frequency spectrum was being allocated by the International Telecommunications Union. Lower frequency space was already occupied by many different communication media and users.e microwave frequency band extends from just about 1 GHz to 30 GHz and above. The nomenclature used is listed here:
Band Nameequency Range (GHz)R>L:.53 - 2.70R>S:.50 - 2.70R>C:.40 - 6.425R>X:.25 - 8.40R>Ku:0.95 - 14.50R>Ka:7.7 - 21.2R>K:7.5 - 31.0R>