696 Magnetic Oscillators as Radiators in Wireless Telegraphy. 



experiments are that the inductive effects observed between the 

 closed oscillatory circuits used are in the main due to electro- 

 magnetic induction and not to true radiation. Secondly, that 

 the most advantageous position o£ the coils is with the plane 

 of the coils parallel to the earth's surface and at a small 

 distance above it. Thirdly, that the increase in the area of 

 the coils is especially advantageous, and that therefore the 

 coils used should consist of single turns of wire enclosing as 

 large an area as possible. Fourthly, that the inductance and 

 capacity of the circuit must be kept low to keep up the 

 frequency. Lastly, the spark method of exciting the oscil- 

 lations can be advantageously employed. 



The best method, therefore, for constructing and using 

 such closed circuit antennae for high-frequency closed circuit 

 wireless telegraphy which seems to be indicated by the 

 foregoing experiments is as follows : — 



In some large field set up a number of short wooden posts 

 having telegraphic insulators attached to them. Round these 

 lay a number of wires, which may be bare copper wires, so 

 as to form a closed circuit of one turn of a number of parallel 

 wires, the circuit being say a foot or two from the ground, or 

 if cows, horses, or sheep are kept in the field it may be better 

 to keep it up 7 or 8 feet from the ground. Complete this 

 circuit by a condenser and spark-gap and make provision 

 by a high-tension transformer for exciting oscillations in the 

 circuit. 



In a similar distant and syntonised circuit include any of 

 the receiving devices now employed in radio-telegraphy, and 

 signals can be transmitted and received without high antennae 

 and without interruption to commercial telephonic circuits. 

 Such closed horizontal receiving circuits will not pick up 

 signals from the vertical antenna transmitters commonly 

 used. 



The method suggested is in fact the old form of magnetic 

 induction space-telegraphy, but conducted with electric 

 oscillations in place of the low-frequency currents obtained 

 by an ordinary alternator or interrupted battery-current. 

 On the other hand, direct experiment with low-frequency 

 alternating currents of 5*4 amperes passed through the small 

 coils used in these experiments, showed that no inductive 

 effects detectable at more than a few yards at most were 

 apparent when using an ordinary telephone as a receiver. 

 Even if the whole of the inductive effect is due to simple 

 electromagnetic induction, the use of high-frequency currents 

 is a distinct advantage. 



