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BELL SYSTEM TECHNICAL JOURNAL 



is 13 kilocycles from fundamental frequencies at 21 and 17 kilocycles. 

 In these measurements both fundamental currents were changed simul- 

 taneously so as to be kept equal throughout. The approach to 

 saturation at currents above ten milliamperes is apparent on these 

 curves ; below, the distortion voltage is proportional to the square of 

 the current. 



The measured curves are seen to agree well with the calculated ones 

 in every instance, confirming theoretical values of* the products within 

 close limits. Eddy currents were negligible in all these coils because 

 of the dust cores. The use of the formulae to determine important 



2 70 



0.5 1 2 3 4 5 10 20 



EACH FUNDAMENTAL CURRENT IN MILLIAMPERES 



Fig. 8 — Thirteen-kc. third order product of equal currents at 21 and 17 kc, permalloy 

 dust core. ;uo = 75, j- = 0.41, Lo = 5.45 mh.,77 = 36.0 /. 



intermodulation products from the constants of the coils therefore 

 seems to be justified. 



Correlation with Single- Frequency Results 



In the single-frequency case Peterson found the resistance and 

 reactance at a fundamental frequency w/Itt to be increased by 



oir fJLo 



AX(co,n) = 2coLn — 77, 

 Mo 



