IMPROVEMENTS IN COMMUNICATION TRANSFORMERS 141 



Q 6 



i/i 5 



50 



500 1000 



FREQUENCY IN CYCLES PER SECOND 



10,000 



Fig. 6 — Curves showing the transmission loss-frequency characteristics of (^4) the 

 small output transformer and (5) the larger output transformer shown in Fig. 5. 



.52 

 ) 



) 

 44 



,40 



36 



32 



28 



30 



500 1000 



FREQUENCY IN CYCLES PER SECOND 



10.000 



Fig. 7 — Voltage amplification-frequency characteristic of an input transformer 

 similar in size to the smaller output transformer shown in Fig. 5. 



Extension of Range to Higher Frequencies. 



The effective permeabilities of alloys of high initial permeabilities 

 drop rather rapidly with frequency, a property which lessens the value 

 of such alloys in transformers for carrier and higher frequencies. This 

 effect, which is attributable primarily to eddy currents, can be greatly 

 decreased, of course, by the use of thinner laminations. The use of 

 these alloys, however, is limited by the rapidly increasing cost of 

 reducing the lamination thickness and the less efficient use of the 

 volume available for the core. This dropping off^ of effective permea- 

 bility with frequency is not so important in audio-frequency trans- 



