APPLICATION or WIRE TRANSMISSION TO RADIO 137 



carrier comes in merely at the rerei\inp: end, in the detector, as a 

 means for translating the side band from radio frequency back to 

 audio frequency. 



This will be made clearer by reference to Fig. 9. At the bottom 

 of the figure is shown schematically a one-way radio system. Above 

 it is depicted the voice-frequency band, showing the manner in which 

 it is shifted by modulation up to the carrier frequency range, and at 

 the receiving end, by detection, back to the voice frequency range. 

 The voice frequency band, as it comes out of the ordinary telephone 

 transmitter, is shown at (61) at its normal telephone-frequency posi- 



RADIO TRANSMISSION WITH CARRIER AND SIDE BAND SUPPRESSION 



_i_j 



1 r Band . 

 Transmitted 



Fig. 9 



tion. Upon modulation with the carrier the reference point of the 

 voice frequency band is shifted from zero frequency (direct current) 

 up to the carrier frequency as shown at b^ where the two side bands 

 appear. The effect of modulation is, therefore, simply to shift the 

 band of signaling frequencies upward in the frequency range and 

 refer it in a double relation to the carrier frequency. 



Located between the upper and lower side band in the figure, 

 there is indicated the unmodulated component of the carrier. The 

 fact that this component is unnecessary so far as the actual intelli- 

 gence-carrying energy is concerned, is proven by the fact that it 

 need not be transmitted to the receiver. The carrier may be sup- 



