. The Bell System technical journal. Telecommunication; Electric engineering; Communication; Electronics; Science; Technology. APPLICATION OF WIRE TRANSMISSION TO RADIO 119 which simply expresses the fact that, as the wave proceeds along the wire, the losses in the resistance of the conductor and in the insu- lation, extract for each mile a certain definite proportion of the volt- age and current which arrives at that point. After traveling (/) miles the original current /i is attenuated down to a value /i«~"' which represents the received current h- This is the same general law of dampin
. The Bell System technical journal. Telecommunication; Electric engineering; Communication; Electronics; Science; Technology. APPLICATION OF WIRE TRANSMISSION TO RADIO 119 which simply expresses the fact that, as the wave proceeds along the wire, the losses in the resistance of the conductor and in the insu- lation, extract for each mile a certain definite proportion of the volt- age and current which arrives at that point. After traveling (/) miles the original current /i is attenuated down to a value /i«~"' which represents the received current h- This is the same general law of damping as applies to the dying down of the voltage and cur- rent in an oscillation circuit, except that here the damping is with respect to distance along the line rather than time. We are assuming, of course, that the circuit is so terminated as to avoid reflection effects at the terminals—a condition readily met, by making the terminal impedance equal to the characteristic line impedance. This is indicated in the figure by the designations, Z (internal) equals Z (line). A similar relation is taken for the radio case. The " line " impedance is here the antenna radiation resistance while the " termi- WIRE AND RADIO TRANSMISSION SYSTEMS. nal " impedance is the resistance internal to the antenna and the apparatus, assuming resonance; thus R (internal) equals R (radiation). We know that in radio there are tw^o distinct causes of the trans- mission loss: (1) that, due to the spreading out of the waves, which is characteristic of non-guided wave transmission; and (2) that due to absorption in the air and earth's surface, which extracts a definite percentage loss for each mile of the radio circuit and which conforms, therefore, to an exponential law similar in its general nature to that of wire attenuation. This transmission law, as expressed by the familiar Austin-Cohen. Please note that these images are extracted from scanned page images that may have been digital
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
