Filters for a 150-Kc Carrier System

This paper describes the filters developed for use in subdividing a frequency band of approximately 150 kc into 32 voice bands, each 3,000 cycles wide. A system of modulation in which each successive stage carries twice the number of voice bands found in the preceding stage reduces to six the total number of different frequency bands requiring separation by means of filters. Economy in cost and mounting space is attained through use of filter types which minimize the number of inductive elements required. Highly stable powdered iron cores are used in all inductive elements.