. The principles underlying radio communication . tube, whichmay be pasteboard, wood, fiber, one of the materials calledbakelite, or some other material. The wire is covered withan insulation of silk or cotton and is sometimes stranded. Acommon type of receiving transformer is shown in Ifig. is often called a loose cpupler. The points of the 444 RECEIVING APPARATUS. switches are connected by tap wires to the turns of the wire inthe coils. On the primary one switch usually takes care ofsingle turns, and the other switch makes contact to groups ofperhaps 10 turns each. To cover 100 turn
. The principles underlying radio communication . tube, whichmay be pasteboard, wood, fiber, one of the materials calledbakelite, or some other material. The wire is covered withan insulation of silk or cotton and is sometimes stranded. Acommon type of receiving transformer is shown in Ifig. is often called a loose cpupler. The points of the 444 RECEIVING APPARATUS. switches are connected by tap wires to the turns of the wire inthe coils. On the primary one switch usually takes care ofsingle turns, and the other switch makes contact to groups ofperhaps 10 turns each. To cover 100 turns of coil, for example,one switch used for coarse adjustment would have 9 points of10 turns each and a zero point, making 10 points in all, and theunits switch w^ould also have 9 points and a zero point. Thenany number of primary turns from 0 to 100 turns could beused. If the primary had 400 turns, the first switch in groupsof 20 turns could have 20 points, including zero, and the unitswitch could also have 20 points for 19 unit turns and Fig. 249.—Receiving transformer. Other arrangements can be used. In the receiving transformershown in Fig. 249 one primary switch has 34 turns betweenpoints, and the other switch has 2 turns between points. Thesecondary switch adjusts by groups of turns; fine tuning isaccomplished by a variable condenser. The coupling betweenthe primary and the secondary is loosened by pulling the sec-ondary out of the primary. The switches of the transformerare adjusted until the approximate wave length range of thestation which it is desired to receive is reached. The secondarycircuit is then tuned by a variable condenser to the stationwhich it is desired to receive. Some coils used in radio receiving sets have more than onelayer. Fig. 250 shows a coupling coil with a type of winding INDUCTANCE COILS. 445 which resembles a lattice. This type of coil is variously called lattice wound, cellular, basket wound, slightly modified form, in whi
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Keywords: ., bookcentury1900, bookdecade1920, bookpublisherwashi, bookyear1922
