88 BELL SYSTEM TECHNICAL JOURNAL 



Fig. 6.22 shows a plot of this for the case of a GT crystal designed to operate 

 at 164 kilocycles. All the information shown in this figure is obtained 

 directly from Fig. 6.21. Since a change in thickness will not have any 

 effect upon the length and width extensional modes of vibration and only 



120 



0.075 0.08 



t IN CENTIMETERS 



Fig. 6.22 — Flexure and extensional resonances in a 164 kc Gr-cut quartz plate. 



changes the flexure frequencies, it would be reasonable to suppose that some 

 thickness could be obtained where no flexure along the length or width 

 would be of the same frequency as the length or width extensional mode. 

 Examining the curves of Fig. 6.22, we find that a thickness of .06 cm., 

 .075 cm. or .085 cm. would meet these conditions. 



