322 



hull: transmitter of modulated waves 



and supplying the same antenna with the same efifective antenna 

 current. Although the logarithmically modulated wave train 

 persists only about one-twelfth as long as the sinusoidally modu- 

 lated wave train, yet it rises to a peak value over thirteen times 

 as great. In order to give some idea of their relative number of 

 radio-frequency oscillations per cycle the vertical lines have been 

 so spaced that each one represents a complete radio-frequency 

 cycle. 



«o- 



60- 



Lo^ariihmic 

 Modulation 



ENVELOPES OF ff/IDlO FR€QU£NCY /INTSNNJf 

 CURRENTS HAVING S/tM£: ff.Af.6. V/ILUC 



la ^^ /Jrnperes RMS. 

 X ■- 535 Meters. 



■« 560,000 cyc/es 

 A/ = SOO y/eye trains per seconds 

 6 -- .089 



Time, seconds x JO'* 

 Fig. 2 — Comparison of antenna currents from spark transmitter and modulated- 



wave transmitter. 



It is not to be inferred from this diagram that the trains of 

 voltage waves applied to the rectifier in a receiving circuit have 

 an envelope precisely similar to the exponential envelope shown 

 here for the wave train transmitter from the spark set. Nor 

 should the assumption be made that diaphrams of the receiving 

 telephones when acted upon by a strong voltage impulse lasting 

 for one ten-thousandth of a second are distorted a proportion- 

 ately greater amount than when acted upon by a weak impulse 



