By Joseph L. Stern, Stern Telecommunications Corporation
Cable companies introduced converters into the homes of cable subscribers in the mid-sixties to eliminate direct pickup interference (DPU). As cable services expanded, converters were redesigned to increase the tuning range of television receivers from the original twelve channels. Since the converter was effectively a gateway for receiving programs that emanated from the headend into the consumer's television set, the redesign a/so provided control over conditional access.
New conditional access control systems such as interdiction, broadband descrambling, or Multipart, when used with cable-ready 7V receivers, do not require the use of converters. At the same time, however, there appeared to be an indication that this combination of new conditional access control systems with an apparent proliferation of cable-ready television sets would substantially eliminate the protection against DPU provided by the converter.
This paper reports on a study commissioned by Cab/eLabs to determine the extent of the DPU problem which may result in a cable television environment operating in the spectrum of 50 mHz to 550 mHz, without converters.
The study predicts that if the present trend of replacing converters with a different type of conditional access control, and the present design of cable-ready television receivers continues, 26.5% of urban/suburban television households will experience DPU problems from VHF television stations if they are served by cable television. The combined transmissions of VHF and UHF television stations in the 50 mHz to 550 mHz band would cause 47.8% of urban/suburban televisions households to experience DPU problems if they are served by cable television.