. Practical wireless telegraphy; a complete text book for students of radio communication . r at a value greater than C, the capacitywhere the reading of the wattmeter falls to one-half thatobtained at Cr and,& = the capacity of the condenser at a similar wattmeter reading corre-sponding to a capacity less than C Although the logarithmic decrement of a transmitter may be measured by several methods,but one considered the most practical by U. S. engineers will be described. To carry out this measurement, a wavemeter fitted with a current indicating instrumentis required, which may be either a h
. Practical wireless telegraphy; a complete text book for students of radio communication . r at a value greater than C, the capacitywhere the reading of the wattmeter falls to one-half thatobtained at Cr and,& = the capacity of the condenser at a similar wattmeter reading corre-sponding to a capacity less than C Although the logarithmic decrement of a transmitter may be measured by several methods,but one considered the most practical by U. S. engineers will be described. To carry out this measurement, a wavemeter fitted with a current indicating instrumentis required, which may be either a hot wire milliammeter or a hot wire wattmeter. The con-denser of the wavemeter should have a chart showing the capacity in microfarads corre-sponding to each position of the pointer on the condenser scale and the hot wire wattmetershould have a range of .01 to .1 watts. To measure the decrement, the wattmeter should be connected as in Fig. 217 for obtainingthe data for plotting a resonance curve. The coil, L, of the wavemeter is then placed in inductive relation to the antenna system. Fig. 221—Kolster Decremeter—the Type Used by the Government Radio Inspectors. at the single turn of wire, L-1. The key of the transmitting apparatus is held down con-tinuously and the length of the spark gap adjusted until the note is clear and uniform. Thisis followed by variation of capacity of the wavemeter condenser until the wattmeter indicatesa maximum deflection which, of course, is obtained at the point of resonancebetween the two circuits. The inductance coil L is then moved about—that is to say—^thecoupling between it and the antenna coil L-1 is changed until the maximum reading of thewattmeter falls (as a matter of convenience) on some even number, say watt. Thecondenser is then set at a lower value of capacity, G, where the reading of thewattmeter is watt. A value of capacity above C is then observed (Ci) where the PRACTICAL RADIO MEASUREMENTS. 203 reading of the wattm
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecttelegra, bookyear1917
