94 



BELL SYSTEM TECHNICAL JOURNAL 



all channels. Th is quantity is plotted in Fig. 10. The insertion loss measured 

 between the input line and the various output lines varied from about 0.5 db 

 in the lowest frequency channel closest to the input to about 1.0 db in the 

 highest frequency channel farthest from the input. This loss is plotted in 

 Fig. 11. Since 0.5 db was approximately the loss observed in each individual 



WAVEGUIDE -X 



WAVEGUIDE CHANNEL FILTERS 



3870 MC 



-TO 

 RECEIVER 



3950 MC 



4030 MC 



10 MC 4190 MC WV 



--TERMINATIONS--' 



-28 -24 -20 -16 -12 -8 -4 4 8 12 16 20 24 

 FREQUENCY IN MEGACYCLES PER SECOND fFROM MID- BAND) 



Fig. 11 — Transmission loss of hybrid branching filter. 



channel dropping unit, it appears logical to assume that the progressive 

 increase in loss is due to passage of the higher frequencies through the lower 

 frequency circuit components. 



The measured discrimination against other channels and image responses 

 was 20 db or more. This modest amount of selectivity is sufficient since the 

 primary function of the present filter is branching, and hence the amount of 



