A HIGH EFFICIENCY RECEIVER 



149 



is comparatively large and the diaphragm for large powers will be 

 driven beyond the point where Hookes' law holds. At the higher 

 frequencies no trouble is to be expected from this source. With the 

 aid of an electrical filter we have therefore made measurements on the 

 harmonic content in the sound output when the receiver was supplied 

 with a sixty-cycle sine wave current. The values so obtained as a 

 function of the power input are plotted in Fig. 9, where curve A is the 



12 3 4 



POWER IN PUT- WATTS 

 Fig. 9 — Power output at 60 p.p.s. 



output power of the fundamental tone and B that of the higher har- 

 monics. These curves show that even at 60 cycles an output power of 

 0.5 watt may be obtained without the introduction of higher harmonics 

 to an amount greater than 1.0 per cent. The total power in the har- 

 monics would in this case be 20 T.U. below that in the fundamental 



