PIERCE. — THEORY OF COUPLED CIRCUITS. 



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dynamometer J). The inductances Z3 and Z4 and their mutual in- 

 ductance were kept constant. Since, however, a single variation at 

 the receiving circuit — namely, the variation of the condenser 64 — is 

 not sufficient to disclose the resonance conditions at the receiving sta- 

 tion, the length of the receiving antenna was also given various values. 

 The results are plotted in the curves of Figure 3, and were obtained as 

 follows: 



With a given length (23.8 meters) of the four-wire receiving antenna 

 the capacity Ci was set at a particular value and the deflection of the 



10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 

 Receiving Capacity 



Figure 3. Family of experimental curves obtained with various heights 

 of antenna (each height giving one of the curves), and various values of re- 

 ceiving capacity C^. 



dynamometer D was read. The capacity C4 was then set at another 

 value and the deflection of the dynamometer was read. Thus keeping 

 the length of antenna at 23.8 meters, I took the readings of the dyna- 

 mometer for a whole series of values of C^. The results are shown in 

 Curve 1 of Figure 3, in which the deflections of the dynamometer (cur- 

 rent square) are plotted against values of "receiving capacity " C4 (in 

 arbitrary units). We shall call this kind of a curve a " resonance 

 curve." When this resonance curve (Curve 1) was completed, the 

 antenna was shortened to 20.8 meters and a second resonance curve, 

 Curve 2, Figure 3, was taken. Again shortening the antenna succes- 

 sively to 17.8, 15.8, 14.8, 13.8, and 12.8 meters, I obtained the curves 

 3, 4, 5, 6, and 7 respectively of Figure 3. 



From this it is seen that for each particular capacity of the antenna, 

 varied by varying the length, there is a characteristic capacity C* that 



