302 BELL SYSTEM TECHNICAL JOURNAL 



current from the output of the transformer would be 



^° = 140X^17:5 = 70' (^^) 



where e is the voltage applied to ground at the common point. The 

 voltage across the output should be 



eo=^Xl7.5=|. . (65) 



But this is just the voltage that should occur across the voltmeter V\. 

 Hence the difference in reading between F2 and Vi will be a measure 

 of the loss introduced by the transformer. From Fig. 13 we see that 

 this is in the order of 0.1 db, which represents a small loss for a 

 transformer. 



Several of the narrow-band filters of the type shown in section V, 

 Fig. 9, have also been constructed and tested. One of these has been 

 used on an experimental radio system at Green Harbor, Massachusetts, 

 since 1935, for the purpose of connecting a transmitter and receiver on the 

 same antenna. This filter has been constructed and tested by Messrs. F. 

 A. Polkinghorn and N. J. Pierce using the design data developed here. 

 The filter used consisted of three sections of the type shown in Fig. 9 

 connected in tandem. The resulting invSertion loss of the filter and 

 associated transformers is shown in Fig. 15. The loss at mid-band is in 

 the order of 1 db and an insertion loss of over 50 db is obtained 2 

 megacycles on either side of the center of the pass band. 



