Vestigal Sideband Subchannel for Multichannel FM Broadcasting

The General Electric Company has expanded the two channel FM stereo broadcast system into a 4-channel one that provides compatibility with present stereophonic and monophonic FM broadcast receiversl. The system exhibits equal noise characteristics at each of the receiver output terminals and allows the use of the Subsidiary Communication Authorization (SCA) channel within the present 200 KHz channel allocations. The system transmits the full audio frequency range of 30 to 15000 Hz on each of the four audio channels and maintains in excess of 30 db audio separation between each of them. Figure 1 shows the total baseband utilization. In this paper, attention will be given to the 76 KHz subchannel with the unique vestigial sideband feature.