By David Large, Gill Industries
At the 1985 NCTA Convention, Gill Cable described an ongoing project whose objective was the development of a dramatically improved system response test instrument. The report outlined the limitations of current high level and low level sweepers and proposed a new "smart" system which could overc£me the limitations of the previous methods.
Gill was motivated in this development by the lack of satisfactory options available to it in doing its own testing. An increasing number of complaints related to the use of high-level sweep made it imperative that less intrusive testing be done. A lack of accuracy available with other products on the market dictated a new approach to response measurement.
In the intervening three years, continued work at Gill has resulted in the development of a successful prototype sweeper with high resolution, fast refresh time and total absence of interference. In field trials it achieved noise-free displays at the maximum cascade of the Gill system (40 amplifiers), electronic error correction, and 0.05 dB of screen resolution. The transmitter generated no complaints of interference in over a month of continuous operation. A patent has been issued in recognition of the uniqueness of the Gill approach.
Although there have been recent product announcements by several vendors in this field, it is felt that there are still serious limitations to all of the newly available approaches. Their dependence on the stability of video carriers at the headend severely limits their usefulness as precision alignment tools in Gill's view.