 or collect. The term antenna gain refers to how much energy is radi- ated, and how concentrated it is in a desired direction compared with an omnidirectional, simple antenna element. For example a typical TV antenna gain is 10 dB and a base station antenna gain is 18 dB. The satellite antenna gain can be in the order of 60 dB or more. Figure 10.3 Different antennas (from left to right) for satellite, TV reception and a mobile communi- cations base station. Source: NASA (public domain): https://commons.wikimedia.org/wiki/File%3AC- band_Radar-dish_Antenna.jpg Terrestrial Broadband Wireless Telecommunications The signal loss of the medium is a function of frequency, and dependent on whether a line- of-sight exists between the transmitter and the receiver. For example, signal path loss in free space where nothing blocks the path between transmitter and receiver is much smaller com- pared with a system operating over a terrestrial channel where a number of physical objects may block or reflect a signal. The block diagram of a wireless digital communications system in Figure 10.2 also shows components necessary for source coding, channel coding of source information. A pre-equaliser/ processor block is necessary to compensate for variations of signal as it propagates through the communication medium. The signal energy in the form of electromagnetic waves is then radiated using antennas. The receiver antenna absorbs a portion of the radiated energy and delivers it to equipment which further processes the signal. Processing is required to reduce signal distortions introduced by the channel, before demodulation and decoding processes are performed to extract the transmitted information. Wireless communications may be point-to-point, such as between the Earth station and a satellite, or point-to-multipoint such as from a satellite to many Earth stations. Communication may also take place in a single direction, called simplex or half duplex (when communication is in one direction at any one particular time). Examples are b