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BELL SYSTEM TECHNICAL JOURNAL 



efficient, which is about 25 parts per million per degree C, does not change 

 appreciably with changes in width. For a +5° plate vibrating in its 

 flexure mode, Fig. 14.7 illustrates measurements made on the variation of 

 temperature coefficient with ratio of axes. For all these X-cut crystals, 

 it mav be observed that deviations of 1% in the width dimension will not 



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200 



100 



50 



20 



10 



.15 



.5 .6 .7 .8 .9 1. 



RATIO OF WIDTH TO LENGTH 



Fig. 14.6. — Inductance of the crystal units used in filters as a function of the cuts of the 

 plates and their ratio of width to length. 



change the temperature coefficient by more than 5%. Such changes 

 are usually negligible. 



14.23 Internal Defects 



Internal defects in the quartz plates may have a large effect on their 

 electrical characteristics. These defects vary so widely in type, size and 

 concentration that it is impossible to predict the effects quantitatively. 

 General comments regarding the results that may be expected for various 



