. An elementary book on electricity and magnetism and their applications. oooo oooc Fig. 408.— Inverted L aerial, which is almost universally used for ship service. yet become standardized. Nevertheless, there are certainpieces of apparatus which are easily recognized in any radiostation. The most striking feature of the equipment is doubt-less the aerial or antenna, which is the elevated wire used toemit or intercept electric waves. The aerial usually con-sists of four or more parallel wires running up nearly verticallyinto the air and usually connected to a set of horizontal wires,as shown i
. An elementary book on electricity and magnetism and their applications. oooo oooc Fig. 408.— Inverted L aerial, which is almost universally used for ship service. yet become standardized. Nevertheless, there are certainpieces of apparatus which are easily recognized in any radiostation. The most striking feature of the equipment is doubt-less the aerial or antenna, which is the elevated wire used toemit or intercept electric waves. The aerial usually con-sists of four or more parallel wires running up nearly verticallyinto the air and usually connected to a set of horizontal wires,as shown in figure 408. These wires are carefully insulatedfrom the supporting masts and separated by spreaders. Forexample, on the U. S. S. Dolphin there are 6 wires 2 feet apart ELECTROMAGNETIC WAVES 557 Copper Ribbon. Fig. 409. — Helix of oscillation trans-former. with a flat top 140 feet in length and 136 feet above the operat-ing room; this gives a total length of 276 feet and a naturalwave length of 330 meters. The oscillation transformercommonly consists of a largehelix made of copper ribbonmounted on an insulatingframework such as is shown infigure 409. The spark gap forsmall amateur sets is usuallymade of two zinc rods mountedas in figure 410. In the largersets used for commercial workthe rotating spark gap, which isattached to the shaft of thealternator, or the quenchedspark gap (Fig. 411) is now com-monly employed. This so-called quenched gap is madeup of a number of accuratelyturned copper disks, which areseparated by annular rings of Fig. 4iomica or oiled silk about thick. The spark is con-fined to the air-tight spaceinside the mica rings. By usingthe proper number of disks inseries this gap gives one dis-charge for each alternation ofthe current and thus produces apure music
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectmagnetism, bookyear19
