By John G. Staiger, Magnavox CATV Systems, Inc.
The cable TV industry is struggling through the process of securing their systems from radio frequency interference. (RFI) Most important is complying with the new FCC rulings. Radiation from the cable television system is a problem which must be dealt with to protect ourselves from the liability which could occur should excessive radiation be found by the FCC field audits.
There are several systems in operation today that purchased equipment (mostly passive products) which did not contain wire meshed-type gaskets for the purpose of improving the RFI shielding characteristics. Recent testing has shown that some systems may measure egress from their system above the FCC limits and the signal leak has been traced back to units not having RFI gaskets. Several devices were tested including trunk. line extenders, splitters, directional couplers, and taps. Several manufacturer's were quantified both with RFI gaskets and without. Testing was performed at the approved FCC site located at Magnavox's facilities in Knoxville, Tennessee.
The scope of this discussion is to address the electronic equipment and not other factors such as quality of installation. connectors. and cable quality. This paper will explain the physical testing facilities, test equipment setup and procedure, results of testing, and suggest some solution to potential problems.