Since a satellite is positioned in a geosynchronous

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Unformatted text preview: rounded by a PVC insulation over which a sleeve of copper mesh is placed. The metal sleeve is again shielded by an outer shield of thick PVC material. The signal is transmitted by the inner copper wire and is electrically shielded by the outer metal sleeve. Coaxial cables offer much higher bandwidths than UTP cables and are capable of transmitting digital signals at rates of 10 mega bits per second. They are extensively used in long distance telephone lines and as cables for cable TV. They are also used by telephone companies to transmit data. In many cases, several coaxial cables are packaged into a very large cable that can handle over 40,000 telephone calls simultaneously. Furthermore, coaxial cables have much higher noise immunity and can offer cleaner and crisper data transmission without distortion or loss of signal. Microwave System Another popular transmission media is microwave. This is a popular way of transmitting data since it does not I incur the expense of laying cables. Microwave systems use very high frequency radio signals to transmit data I through space. However, at microwave frequencies, the electromagnetic waves cannot bend or pass obstacles like I hill. Hence it is necessary that microwaves transmission be in a line-of-sight. In other words, the transmitter and I receiver of a microwave system, which are mounted on very high towers, should be in a line-of-sight. This may I not be possible for very long distance transmission. Moreover, the signals become weaker after traveling a certain distance and require power amplification. In order to overcome the problem of line-of-sight and power amplification of weak signals, microwave systems use repeaters at intervals of about 25 to 30 kms in between the transmitting and receiving stations (see Figure 17.5). The first repeater is placed in line-of-sight of the transmitting station and the last repeater is placed in line of-sight of the receiving station. Two consecutive repeaters are also placed in line-of-sight of each other. The data signals are received, amplified, and retransmitted by each of these stations. Microwave...
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