The AR6A Single-Sideband Microwave Radio System: Prologue

Prologue By R. E. M A R K L E * (Manuscript received January 27, 1983) The AR6A Single-Sideband Amplitude Modulation (SSBAM) Transmission System makes very efficient use of the radio spectrum by transmitting 6000 message circuits in a 29.65-MHz radio channel. This capability is achieved by maintaining a tighter frequency spacing of the multiplexed mastergroup signals and by discarding redundant sideband signals before transmission over the radio path. The AR6A System can provide a maximum capacity of 42,000 message circuits for the 6-GHz portion of the radio network when all eight channels are utilized. This capability, combined with the alternate use of the 4-GHz spectrum for message or digital circuits, provides the proper mix of network capability choices. This introduction gives an overview of the AR6A System and a brief history of single-sideband evolvement in the Bell System. It also is a prologue to the papers in this volume, which describe some of the specifics of the system design. I. INTRODUCTION On J a n u a r y 12, 1981, t h e first AR6A + Microwave Radio System was placed in service between Hillsboro, Missouri, a n d La Cygne, Kansas. T h i s event marked the first application of single-sideband transmis- * Bell Laboratories. The AR6A designation represents Amplitude Modulation Radio at 6 GHz for the initial (A) version of the system. °Copyright 1983, American Telephone & Telegraph Company. Photo reproduction for noncommercial use is permitted without payment of royalty provided that each reproduction is done without alteration and that the Journal reference and copyright notice are included on the first page.