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BELL SYSTEM TECHNICAL JOURNAL 



The theoretical band width for this type transformer is given ap- 

 proximately by the expression 



/2-/1 



fm 



^(X + 2) 



(62) 



Such a transformer is also suitable for connecting together vacuum 

 tubes of high impedance. 



Another type of transformer of some interest is one which will 

 transform from very high impedances to very low impedances. Such 

 a transformer is shown in Fig. 11. It has a shunt conductor on the 

 high-impedance end and a series conductor on the low-impedance end. 

 Such a transformer does not have a constant transformation ratio over 

 the whole band, but for about 80 per cent of the theoretical band width 



^//fffjjj77J-j-77//^Trrr 



^0, 



C| 



l2 



J 



Fig. 11 — A series shunt type transformer suitable for wide bands. 



the transformation ratio is approximately constant. The design equa- 

 tions for such a transformer are 



(63) 



The transformer is especially useful since it will give the widest trans- 

 mission band for a given transformation ratio of any of the trans- 

 formers discussed. 



Many other types of filters, transforming and nontransforming, are 

 also possible using transmission lines and condensers. A partial list 

 of such filters is shown in Fig. 12 together with their attenuation and 



