. Practical wireless telegraphy; a complete text book for students of radio communication . lculation or by actual measurement. 170. Calculation of the Decrement of the Wavemeter (or Decremeter).—One method by which the damping of the wavemeter may be determined is car-ried out as follows: After the value of Si -)- Si is obtained, the coupling between the wavemeter coil and theantenna system must not be altered. A piece of resistance wire, R (Fig. 217), is stretchedtightly between two binding posts and connected in series with the circuit of the amount of wire in use is gauged by
. Practical wireless telegraphy; a complete text book for students of radio communication . lculation or by actual measurement. 170. Calculation of the Decrement of the Wavemeter (or Decremeter).—One method by which the damping of the wavemeter may be determined is car-ried out as follows: After the value of Si -)- Si is obtained, the coupling between the wavemeter coil and theantenna system must not be altered. A piece of resistance wire, R (Fig. 217), is stretchedtightly between two binding posts and connected in series with the circuit of the amount of wire in use is gauged by the sliding contact, T-1. (A piece of No. 28 Germansilver wire or Therlo wire about IS inches in length will be found satisfactory.) With the pointer of the condenser set at Cr, or resonance, the spark gap is energized andresistance added at R until the reading of the wattmeter falls to exactly one-half thatobtained in the original resonance adjustment, or watt. The condenser of the wave-meter is then shifted to either side of resonance to such a value of capacity that will give. Fig. 222—Rear View of Kolster Decremeter. one^half the wattmeter reading obtained at Cr, viz., watt. Let the capacity of the wave-meter condenser below resonance be represented by Ca and the capacity above resonance by- Then the following formula is applicable: c. o. 5i -4- 62 -I- 63 : X (6) Now, Sa is the decrement due to the addition of the resistance R, and it is evident that ifthe value of Si -|- 82 is subtracted from Si _|_ Sa _|- Sa, the value of Sa is at once obtained. It has been shown by Fleming and others that if the value of S2 is thus found out, we mayevaluate the decrement of the wavemeter S2 by the following formula: Letting V stand for the value obtained in equation No. 5 and Vi for the value in No. 6, then, V X s» «2= (7) 2V — Vi 204 PRACTICAL WIRELESS TELEGRAPHY. Hence, by subtracting the value of 5s from S» -|- 5a we have 5i, the decrement of the aerialcircuit
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