Wide-Band Open-Wire Program System

HE simultaneous broadcasting of the same radio program from a large number of broadcasting stations, in different sections of the United States, has become of such everyday occurrence that the radio listening public takes it as an accepted fact and in many cases does not know whether the program is originating in the studio of a local broadcasting station or in a broadcasting studio in some distant city. T h e wire line facilities furnished by the Bell System for the interconnection of the radio stations, particularly the wire line facilities in cable, have such transmission characteristics t h a t little detectable quality impairment is introduced even when programs are transmitted over very long distances. This cable program system was described in a recent paper. 1 More recently a new program system for use on open-wire lines, which possesses transmission characteristics comparable with those of the cable system, was developed and an extensive field trial made involving two circuits between Chicago and San Francisco. This paper describes this new open-wire program system and gives the principal results of the tests made on the two transcontinental circuits. In the paper referred to describing the cable system, the various factors and considerations involved dictating the grade of transmission performance that is desired for program circuits were discussed in considerable detail so they will not be reviewed here. T h e transmission requirements chosen as objectives for both cable and open wire are as follows: Frequency Range Frequency range to be transmitted without material distortion-- about 50 to 8,000 cycles.