FILTERS FOR CARR/FR SVSTF.\fS 



199 



In Fig. 7 the two large cylindrical containers parallel to the panel house 

 eleven of the balanced quartz crystal elements. The smaller cylindrical 

 cans contain adjustable retardation coils while the rectangular cans house 

 fixed coils. Adjustable air capacitors can be seen mounted on the hard 

 rubber plate between the two crystal units. 



The adjustment side of the brass panel is e.xposed in Fig. 6. Screwdriver 

 adjustment of the retardation coils is possible through the circular holes at 



-12 



-to 



-6 



-2 



2 4 



(CARRIER) 

 FREQUENCY IN KILOCYCLES PER SECOND (FROM 88-KC CARRIER) 



Fig. 2 — The insertion loss-freciuency characteristic of the filter. 



- -9 -8 -7 -6 -5 -4 -3 -2 -1 



FREQUENCY IN KILOCYCLES PER SECOND (CARRIER) 



(FROM 88-KC CARRIER) 



Fig. 3 — Enlarged insertion loss-frequency characteristic of the filter pass band. 



the top left and right of the panel. The rotors of three of the four air 

 capacitors are visible inside the square cut-out in the panel. The panel in 

 the lower half of the filter contains the remaining elements mounted and 

 wired in a similar manner. 



The schematic which was found to be most useful during the design of 

 the filter is shown in I-'ig. 8. Thus the electrical circuit consists essentially 

 of two comple.x lattice sections sei)arated by one constant-k ladder section 



