Importance

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Abstract

A method to discover defective coaxial shielding in cable lines in a building by inducing a test current into the nearby alternating current (AC) power lines (also known as “mains” in the United Kingdom) and measuring a resulting induced test signal inside the coaxial cable lines. A test signal current driven onto the power lines from a wall socket will propagate back to the main electrical box in the building. The main electrical box is normally connected to a ground, such as water pipes or a ground rod driven into the earth. Some of the test signal will be transferred to the outside of the coaxial cable in the building by radiation, conduction or induction. If the coaxial cable has perfect shield integrity, none of the test signal will be induced into the center conductor of the coaxial cable. However, if the coaxial cable has poor shielding integrity or a shield break, some portion of the test current will be transferred into the inside of the cable, potentially causing interference with cable signals. A broadband test signal can be intentionally driven onto the building's power lines and measured at a convenient location in the building's coaxial cable, such as at the tap, the ground block, or inside the house. Optionally, the test signal can propagate back to the headend where it can be observed and measured. A display from the headend, such as spectrogram showing the test signal's interference, can be relayed back to the field where the test result can be viewed by a technician. Methods are disclosed to reduce interference of the test signal with upstream data signals.

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First Claim