. Practical wireless telegraphy; a complete text book for students of radio communication . lephone P, causing the telephone diaphragm to vibrate at a rate corresponding to the spark frequency of the transmitter. 128. Other Methods of Coupling.—If the open and closed oscillation cir- cuits of a receiver are coupled throughan auto-transformer as in Fig. 151, thetwo circuits are then said to be di-rectly or conductively coupled. In this system part of the turns of asingle coil constitute the primary cir-cuit and part the secondary circuit; theturns between the points A and B may beconsidered as
. Practical wireless telegraphy; a complete text book for students of radio communication . lephone P, causing the telephone diaphragm to vibrate at a rate corresponding to the spark frequency of the transmitter. 128. Other Methods of Coupling.—If the open and closed oscillation cir- cuits of a receiver are coupled throughan auto-transformer as in Fig. 151, thetwo circuits are then said to be di-rectly or conductively coupled. In this system part of the turns of asingle coil constitute the primary cir-cuit and part the secondary circuit; theturns between the points A and B may beconsidered as the primary winding of thetuner, while those from B to C may besaid to constitute the secondary the oscillation frequency of the an-tenna circuit can be increased or decreasedby the variable contact A and similarlyfor the detector circuit by contact C. Fun-similar to the inductively coupled receiverwith the exception that part of the current induced in the antenna circuit flows directlythrough the shunt path afforded by the detector circuit. The disadvantage of this method. Fig. 152—The Capacitively Coupled Receiver,damentally the operation of this apparatus 134 PRACTICAL WIRELESS TELEGRAPHY. of coupling is that any change of wave-length adjustment of the open and closed circuitschanges the coupling, but this can be prevented by connecting an aerial tuning inductancein series with the primary winding. The primary and secondary windings may be looselycoupled at any particular wave length adjustment, by adding turns at the aerial tuninginductance and taking them out at the primary winding. This will decrease the mutualinductance of the two circuits and therefore will reduce the coupling. The method termed the capacitive coupling is shown in the diagram of Fig. 152. Theprimary and secondary coils shown at L-1 and 1^2 are not in direct inductive relation.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecttelegra, bookyear1917
