Wireless Telegraphy and Telephony

 CHAPTER V. TUNING AND COUPLING, DIRECTIVE WAVE TELEGRAPHY. Tuning has been mentioned in several places but not explained in any greater measure than was necessary to render a conception which would enable the reader to follow the text intelligently in order not to depart from the subjects under discussion there and consequently defeat the purpose of clearness. The great importance and value of properly “tuning” the circuit of radiotelegraphic apparatus cannot be over- estimated and for that reason the subject can hardly be passed without some further explanation. Its effects are two-fold. In the first place it is always desirable and highly important that wireless messages should be, so far as is possible, selective, inasmuch as there are often several stations in the same immediate neighborhood operating at the same time. This result is reached by tuning and it is possible for them all to transmit different messages at the same time without confusion by the proper arrangement of the wave length. The second effect is the transmission of messages over long distances with the comparative con- sumption of small amount of power by adjusting the “pe- riod” or electrical length of the circuits until the oscilla- tions “flow in harmony” with each other and resonance is secured. Perhaps the only way that these results may be made clearly intelligible is by resort to a graphical example. Suppose that a very heavy weight were suspended from a 70