. An elementary book on electricity and magnetism and their applications. gwaves. Inasmuch as most detectors used in radiotelegraphyare of high resistance, they are generally placed in separatecircuits coupled directly or inductively to the antenna. Amongthe many types of receiving circuits used those shown infigure 407 will represent some of those most frequently found 556 ELECTRICITY AND MAGXETISM in practice. The direct-coupled receiving circuit is shown in(1) and the inductive or loose-coupled type is shown in (2).In the latter type the number of turns on both coils Lx and L2can be varied,
. An elementary book on electricity and magnetism and their applications. gwaves. Inasmuch as most detectors used in radiotelegraphyare of high resistance, they are generally placed in separatecircuits coupled directly or inductively to the antenna. Amongthe many types of receiving circuits used those shown infigure 407 will represent some of those most frequently found 556 ELECTRICITY AND MAGXETISM in practice. The direct-coupled receiving circuit is shown in(1) and the inductive or loose-coupled type is shown in (2).In the latter type the number of turns on both coils Lx and L2can be varied, as well as their distance apart; there is alsoa variable condenser C2 bridged across the coil Lv It willbe noticed that in each type a fixed condenser Ci, called a stoppage condenser, is bridged across the telephone so asto permit the oscillatory currents to pass freely through itand to store up the direct-current pulses and discharge themthrough the telephone. 378. Wireless apparatus. The development of radio-telegraphy has been so rapid that the apparatus has not as. 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
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