I- 1 ITERS lOR CAKRIKK SYSTEMS 



201 



and give practically all the discrimiiiution recjuired. It will be noted that 

 the filter uses the equivalent of l.^U electrical elements consisting of 63 in- 

 ductors. 63 capacitors and 4 resistors. 



The use of complex filter sections permits the realization of filter char- 

 acteristics which have low distortion in the pass band and high discrimina- 

 tion outside the pass band with a more efiicient utilization of elements than 

 is possible with a larger number of simpler sections. Improved mathe- 

 matical methods of network analysis developed in the past several years 



Fig. 6 — Exterior view of the tiller with one cover removed. After adjustments arc 

 completed the cover is soldered on to seal the assembly. 



have made the design of such complex tilter sections possible while recent 

 developments of precise and stable filter elements and improved measuring 

 circuits have made it possible to manufacture such filters. 



It has been mentioned before that the use of quartz crystal elements re- 

 stricts the filter band width which can be realized. In the frequency loca- 

 tion selected for this filter (lower sideband of an 88-kc carrier frequency) 

 a complex lattice section of the type shown in Fig. 8, when used alone, will 

 permit the use of physical crystal elements for bands not over 7.^()0 cps 



