THK THAX8ISTOU AS A NKTWOliK KLKMKX'P 



339 



9.3 9.4. 9.5 9.6 9.7 9.8 9.9 10.0 10.1 10.2 10.3 10.4 10.5 10.6 10.7 

 FREQUENCY IN KILOCYCLES PER SECOND 



Fig. 7 — Transmission of M-derived band filters. 



teristics, active filters of this kind appear to offer potential competition 

 to the crystal channel filters used in broad band carrier systems. 



Working Model 



To further emphasize this fact the photograph of Fig. 9 shows a 

 model of a composite band filter designed to transmit a 4-kc band at a 

 midfrequency of 98 kc. This model contains seven miniature, adjustable, 

 ferrite inductors, miniature capacitors, and two n-p-n junction transis- 

 tors. The transmission characteristic is shown in Fig. 10. Hence in some 

 cases by employing active cii-cuitry it is possible to use miniature com- 

 ponents thereby gaining at least an order of magnitude in the size and 

 weight of structure. 



