Wireless Telegraphy and Telephony

 WIRELESS TELEGRAPHY is variable. The primary is adjustable by means of a slider and the secondary by means of a multi-pointed switch. The slider is usually connected to the aerial and one end of the coil to the ground. The detector, etc., are connected to the terminals of the secondary. Variable con- densers may be added with good results to both the primary and secondary circuits. Fig. 93.—Diagram showing position of loose coupler in circuit. Loose couplers also take the form of doughnut tuners in which the secondary revolves instead of slides. The coupling is variable in such an instrument by simply turn- ing the secondary. The wave emitted from a transmitter is in reality made up of two waves of different lengths. The variation in the lengths of these two waves is dependable upon a factor known as the coefficient of coupling. It is almost impos- sible to clearly explain the phenomenon and in order not to confuse and complicate by a rather lengthy explanation it may be well to simply state that its effect is to make selective tuning difficult unless the coupling of the receiv- ing station can be varied to correspond with that of the transmitter and ask the reader to take it for granted. Varying the coupling adjusts the difference in the two