liyPRR-FREQVK\'Cy WAVE Gl'IPES 



297 



The author's experimcMital work on attenuation is still incomplete, 

 but the results to date are altogether in keeping with calculation. 

 Work done at or near cut-off for all four types of waves confirms their 

 descending characteristics at these points. Other more systematic 

 measurements made on the Ih type of wave over a considerable range 

 of frequencies are also in good agreement with calculation. Typical 

 results are shown in Fig. 8. They were made on a straight section of 



1200 1300 1400 



1500 1600 1700 1800 1900 2000 



FREQUENCY IN MEGACYCLES PER SECOND 



2100 2200 2300 



Fig. 8— Attenuation suffered by Hi waves in a 6-inch hollow copper pipe. Curve 

 is calculated. Plotted points are experimental. 



hollow copper pipe six inches in diameter and 1250 feet long. No 

 experimental attenuation data on the H^ type of wave are yet avail- 

 able except at cut-off. It may be argued, however, that the same 

 theory applies to all four forms of waves so that data tending to con- 

 firm the calculated attenuation of one form of wave tends also to 

 substantiate the predicted attenuation for the other forms as well. 



