. The principles underlying radio communication . d for 110 volts,and the secondary for 5,000 to 20,000 volts. By means of thetransformer the condenser C is charged to a high voltage, andstores up energj\ When the voltage becomes great enough itbreaks down the spark gap and the discharge takes place as anoscillatory current in the inductance coil h and its leads. SeeSection 115. The main discharge does not take place throughthe turns of /S on account of its relatively high impedance. The SPARK GAPS. 355 transformer is sometimes still further protected from the con-denser discharge by inserting
. The principles underlying radio communication . d for 110 volts,and the secondary for 5,000 to 20,000 volts. By means of thetransformer the condenser C is charged to a high voltage, andstores up energj\ When the voltage becomes great enough itbreaks down the spark gap and the discharge takes place as anoscillatory current in the inductance coil h and its leads. SeeSection 115. The main discharge does not take place throughthe turns of /S on account of its relatively high impedance. The SPARK GAPS. 355 transformer is sometimes still further protected from the con-denser discharge by inserting choke coils (not shown in ) in the leads between the transformer and condenser. Theseobstruct the high-frequency current, but do not hinder the pas-sage of the low-frequency charging current into the 181 shows a transformer used in radio sets. The standard generator frequency is 500 cycles per causes the condenser to discharge 1000 times a second, oncefor each positive and each negative maximum if the spark gap. Pig. 181.—Step-up transformer for charging condenser. is of such length as to break down at the maximum voltage givenby the transformer. The number of sparks per second is calledthe spark frequency. With the standard spark frequency of1000 per second the amount of power the set sends out is con-siderably greater than it would be at a low frequency like 60cycles per second, because the transmitted radio waves are morenearly continuous, as will be shown later. The radiated wavetrains strike a receiving antenna more frequently and their am-plitude does not need to be so great to produce the same effectas stronger waves received at longer intervals of time. The 356 TRANSMITTING APPARATUS. higher frequency produces a tone in the receiving telephonethat is more easily heard, because the ear is most sensitive tosound waves of about 1000 per second and also the tone is moreeasily heard through atmospheric disturbances. A 60-cycle sup-ply may
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