. Radio, miracle of the 20th century ... a story of human achievement that stands unrivalled in the history of humanity, together with a colorful portrayal, giving a broad, general view of the whole subject of wireless telegraph and telephone and its marvelous development . r and reproduce at the receiver a sound Fig. i ! B ^^ Cbntitiut ws Wave , i i jpl wave, that is, a wave similar in character to that of figure45. It has been possible to do this by varying the ampli-tude of the radiated high-frequency waves so that thisvariation in amplitude follows in detail the wave varia-tion produc
. Radio, miracle of the 20th century ... a story of human achievement that stands unrivalled in the history of humanity, together with a colorful portrayal, giving a broad, general view of the whole subject of wireless telegraph and telephone and its marvelous development . r and reproduce at the receiver a sound Fig. i ! B ^^ Cbntitiut ws Wave , i i jpl wave, that is, a wave similar in character to that of figure45. It has been possible to do this by varying the ampli-tude of the radiated high-frequency waves so that thisvariation in amplitude follows in detail the wave varia-tion produced by the sound. In figure 46, curve A repre-sents a simple sound wave. By means of methods to bedescribed later, the amplitude of a continuous radio wave MIRACLE OF THE AGE 307 is varied so that the variation in amplitude follows iden-tically the amplitude and frequency of the sound is shown by the heavy line in B of figure 46. Thisline, together with lower inclosing line, is called theenvelop of the radio wave. Note that the upper andlower inclosing lines have the same shape. This waveestablishes oscillations identical with it in the receivingantenna. When these oscillations are rectified by thedetector and passed through a telephone receiver the 7b source_ of UndampedO Haves n rectified current is similar to the heavy line of the en-velop. This is necessarily so as the rectified telephonecurrent does not follow the change in each individualradio frequency oscillation, but follows the change in theamplitude of these oscillations. This change is repre-sented by one of the envelop lines as stated. When a radio wave has its amplitude varied so that itsenvelope is made to assume any desired curve the waveis said to be modulated. The instrument or apparatusthat accomplishes this object is called a modulator. The simplest way of modulating a radio wave is bychanging the resistance of the antenna. This change inresistance changes the intensity of high-frequency cu
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Keywords: ., bookcentury1900, bookdecade1920, bookidradiomiracle, bookyear1922
