By Tom Williams, Holtzman Inc. , Longmont, Colorado
Sheath current induction is a method for finding shield breaks in coaxial cable by inducing a broadband test current onto the shield and receiving a center conductor signal when there is a shield break. This test method allows the range to a shield break to be measured, as well as a measure of the severity of the break. This paper correlates the sheath current induction test results for a house with the house's ability to generate impulsive interference with digital upstream traffic. The test method is to first create a known shield break at the ground block and characterize the break by the sheath current induction test. Next, impulsive interference is generated inside the house on the house's power wiring with a noisy 110 volt AC load. This impulsive interference is measured at the tap with a bandpass filter and a totaling counter. Finally, the known shield break is fixed and the test is redone. This test procedure was repeated on a number of different houses.