Radiators in Wireless Telegraphy. 



687 



In the case o£ two small coils placed at a distance large 

 compared with their dimensions the magnetic induction for 

 a steady field should by theory be twice as great in the 

 position (A. A.) as in the position (B.B.), and should be the 

 same in position (C.C.) as in position (B.B). Also zero 

 in the 6 positions (A.B.), (B.A.), (C.B.), (B.C.), (A.C.), 

 (G.A.). 



But when using the high-frequency primary current 

 the secondary current is still large in the cases (A.C.),( B.C.), 

 and (C.B.), viz., when either the receiver or transmitter coil 

 has its plane parallel to the earth's surface. 



Subsequent results showed that the height of the coils 

 above the ground affected this result considerably. Never- 

 theless the exalted effect in position (C.C.) is interesting and 

 convenient because it is easy to construct large circuits out 

 of doors in positions (C.C.) and very much less easy without 

 the aid of tall masts to make them in the positions (A.A.) 

 or (B.B.) . 



Exp. II. Effect of varying distance. Coils vertical. — The 

 same pair of coils were set up on positions (A.A.) and their 

 distances varied. The receiver circuit was tuned to a frequency 

 of 162,000, and the primary current was 4*7 and 54 amperes 

 in two sets of observations respectively. 



Table II. — Coils in position (A. A.). 



Distance of Centres 

 in feet. 



Primary Current 

 in amperes. 



Secondary Current 

 in milliamperes. 



78-0 



5-4 



13-7 



123-5 



„ 



6-46 



170-5 



,, 



1-17 



237-0 



,, 



012 



36-2 



4-7 



41-0 



88-0 



,, 



6-99 



1232 



>» 



3-05 



169-7 



,, 



1-01 



2370 



" 



011 



The results are plotted in the curve in fig. 3. 



