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at the receiving points. Fig. 9 shows data taken in this way. The 

 curve which reaches the highest point shows for a typical summer's 

 day the field strengths received on the long wave from America. The 



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Fig. 9 — Long wave curve and corresponding short wave curve of received field 



strength 



other curve shows the field strengths received on short waves employ- 

 ing three wave-lengths, 16, 22 and 38 meters, and taking for each time 

 of day the one of these which was best suited to the conditions. 



On this typical day all the wave-lengths were operating well. It 

 will be noted, however, that there are times when the long wave is low 

 and some one of the three short waves is more effective and other times 

 when none of the three short waves are high but the long wave is 

 effective. Furthermore, all of these waves vary a good deal so that 

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