When a charge is stationary, it has around it an electrostatic field. Gravity springs from the property of matter we call mass, while electromagnetic effects derive from the property we call charge. It is gravity and particularly electromagnetism that are of direct concern to us in our daily interactions. The two nuclear forces exert their influence over only very very short (nuclear) distances, and apart from holding all matter together do not directly influence us in everyday life. These are, in order of strength, the nuclear strong force, the electromagnetic force, the nuclear weak force and the gravitational force. There are four, and only four known forces in the universe (although the so-called dark energy hints at another). This note discusses the frequencies that are used for space communications. This includes a book, an attractive wall poster and a simplified spectrum graphic.
#Satellite frequency bands uplink and downlink for free#
However, the Australian Communications and Media Authority (ACMA) makes all spectral allocation information available for free download. The ITU unfortunately, charges horrendous prices for any of its publications. The general frequency assignments may be found at the ITU web site, and Australian allocations may be seen at the ACMA web site. In doing this they divide the world into three regions, regions I, II and III. The International Telecommunications Union (ITU) is the global body that assigns radio frequency allocations. Radio frequencies must be shared with terrestrial radio services, and international frequency assignment is essential to avoid interference between all the different uses made of the radio spectrum. Although there have been some experiments in optical communications using lasers, most satellite communication is accomplished by radio, one part of the electromagnetic spectrum. To be useful satellites and spacecraft must communicate, sometimes to relay communications between two points, sometimes to transmit data they have collected. Radio Frequencies for Space Communication RADIO FREQUENCIES FOR SPACE COMMUNICATION
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