. The design and construction of a radio telephone station . y outlook it sseras as if the vacuumtube will supersede all other methods of gener-ating sustained waves, because its ease of con-trol and dependability. JU 3. METHODS IN USE All radio telephone methods consist first,of a source of high frequency alternating current,and second, of some method of modulating thiscurrent so as to produce a wave of high frequency alternating currents may beproduced in the following ways:-1, ArcsZ, Radio-Frequent Sparks 3, Vacuum Tube Oscillators 4. Alternators of Radio Frequency(1) Ar
. The design and construction of a radio telephone station . y outlook it sseras as if the vacuumtube will supersede all other methods of gener-ating sustained waves, because its ease of con-trol and dependability. JU 3. METHODS IN USE All radio telephone methods consist first,of a source of high frequency alternating current,and second, of some method of modulating thiscurrent so as to produce a wave of high frequency alternating currents may beproduced in the following ways:-1, ArcsZ, Radio-Frequent Sparks 3, Vacuum Tube Oscillators 4. Alternators of Radio Frequency(1) Arcs The simplest generator of radio frequengryoscillations of large power is the Dudlell-Poul-sen Arc shown in Figure 2, Here G is a d«c. gen-erator, r is the resistsince controlling the arccurrent, and L is a chok<3 coil for keeping thea. c# out of the generator and also for steady-ing the supply voltage. The Duddell arc, K,has solid carbon electrodes. L, 0, and Rare inductance, capacity, and resistance inserted ? ■ t \ ^l-* -4 Wi:^:.. ■i-m^^m^mmm%. 11 in the arc shunt circuit. Their values must becarefully chosen, If the arc be lit, it is found th atan alternating current appears in the shunt cir-cuit, and if the frequency of this current iswithin the limits of audibility, a pure singingtone will be heard, The arc differs from ordinary conductorsin one essential respect. If we divide thevoltage across the terminals of an ordinarymetallic conductor by the current flowing thruthe conductor, the quotient is found to be aconstant quantity called the resistance of theconductor. This is the case regardless of thevalues of voltage and current (under ordinary con-ditions) , In the arc, the quotient is by nomeans constant. For higher voltage the arc re-sistance is large and very little current passesthru the arc under such voltages. As the voltagedecreases, the resistance decreases greatly, andthe current tends to increase indefinitely up tothe point of a short circuit. We coro
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