By John C. Fan, Frank A. Spexarth
At a time when the cable television industry is absorbing such sophisticated new technologies as laser link and microwave transmission, it may seem unusual to suggest taking another look at a tool as familiar and comfortable as the coaxial cable. Unusual, that is, until you consider the demands likely to be made of this cable during the remainder of the 1970's.
Most observers predict that penetration of cable television into the top 100 cities during this decade will stimulate dramatic changes in both your services and systems. There is talk of 24, 48, 64, or more channels. You will be called upon to transmit not only video signals, but also data and facsmile reproductions. Two-way communications is likely. Average system size will jump from approximately 100 miles of cable per city to as much as 4,000 miles per city.
Such growth places heavy demands on the technical resources available to you. Utilization of laser link and microwave technology is crucial to providing economical service to large metropolitan areas. Yet even such advanced equipment will not eliminate the need to wire with coaxial cable in any system of the foreseeable future. In fact, it is the basic system you know today which will be called upon to provide the many new services upon which your industry will grow. There is little doubt that more sophisticated electronics hardware will become available as your industry requires it. The question is, can your cable keep pace?
The nature of a cable television system makes this a crucial question because noise-to-signal limitations are principally a function of the cable. The most effective way to improve system efficiency is to use cable with lower signal loss rather than to depend on high gain amplifiers which unavoidably are limited by attenuation characteristics of the system's cable. Thus, as the state of the art in active equipment improves, the electrical properties of the coaxial cable become even more significant to the system owner. This paper examines factors which must be considered in producing cable with low signal loss characteristics.