. The principles underlying radio communication . ory antenna can also be constructed, using a suit-able arrangement of wires for the upper plate of the condenserand using for the lower plate a number of parallel wires ele-vated a few feet from the earth and insulated from the connection is then made to the earth itself. The wiresforming the lower plate of the condenser are then called a counterpoise antenna or simply a counterpoise. 7 See Wireless Age, 8, pp. 11-14, April, 1921. 306 ELECTROMAGNETIC WAVES. In reception electric waves reaching an antenna set up analternating en if. bet
. The principles underlying radio communication . ory antenna can also be constructed, using a suit-able arrangement of wires for the upper plate of the condenserand using for the lower plate a number of parallel wires ele-vated a few feet from the earth and insulated from the connection is then made to the earth itself. The wiresforming the lower plate of the condenser are then called a counterpoise antenna or simply a counterpoise. 7 See Wireless Age, 8, pp. 11-14, April, 1921. 306 ELECTROMAGNETIC WAVES. In reception electric waves reaching an antenna set up analternating en if. between the wires forming the upper plate of thecondenser, and the ground or other lower plate of the longer and higher the wires forming the antenna thegreater the einf. produced. As a result of this emf. an alter-nating current will flow in the antenna wires. The energy ofthe current is absorbed from the passing wave, just as some ofthe energy of a water wave is used up in causing vibrations ina slender reed which stands in its FI&.I67-AmFANOR,,HARPANTlNNA. 138. Different Types.—An antenna consisting of horizontalparallel wires supported between two masts and insulatedtherefrom is common. This is a standard form for ship sta-tions. If the lead-in wires are attached at the end of the hori-zontal wires (Fig. 166) the antenna is said to be of the in-verted L type. If the lead-in wires are attached at the centerof the horizontal wires, the antenna is said to be of the Ttype. Both of these types are found at many land stations,including amateur stations. The wires are kept apart by spreaders, which may be of wood. These two types are oftenreferred to as fiat-top antennas. The V type of antenna (Fig. 167) consists of two sets of hori-zontal or slightly inclined wires supported by three masts, so ANTENNAS. oOT that the horizontal portions form an angle. The V type is used tosome extent in military work, but is not much used elsewhere. The fan or harp antenna consi
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