Quick way to see if you have a hot ground -- Measure voltage between the ground at the receptacle where the TV is plugged in (TV turned on) and your water pipe (if metal) where it enters your house. May require a long single conductor wire strung up stairs and across floors between those locations.
Maybe they have a hot ground. What is happening is that the voltage between where their equipment is grounded and where your TV set is grounded is not zero where it should be.
All of your ground wires including that going to th receptacle where the TV is plugged in are supposed to come together in your main breaker panel. Also in the panel (main panel only) all your grounds are tied (bonded; connected) to all your neutrals and also to the (fat) neutral coming in from the utility pole to your house and into the panel. Add to that a continuous (unspliced) ground wire from your panel either to a ground rod or to the main water pipe (if metal) entering your house. If you have the ground rod, add yet one more ground wire, this one can be clamped or spliced to the previous ground wire and the other end is connected to the water pipe. These last two ground wires must be at least #6 for 100 ampere service and #4 for larger (amperage) service. These sizes also apply to wire bridges around water meters, water heaters, and sections of plastic pipe. An entering gas pipe must also be so grounded (bonded to ground) but the system must also include a ground rod grounding or a water pipe grounding.
If "something is hot" when they tie their ground to your water pipe (within 5 feet of where the pipe enters and also before the water meter) then they have the hot ground.
Prior to the coax cable being screwed onto your TV, the shell or shield of the coax is their ground.
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Last edited by AllanJ; 08-08-2010 at 12:30 PM.