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Re: grounding NST's



Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Neal,

There are different opinions on how to ground the NST. Some will say to use mains ground for safety. Some will say use RF ground to keep stuff off the mains ground incase of a flashover to the TC primary or worst yet a strike to the TC primary. I use RF ground and avoid the safety issue by locating my NST's under the TC primary where no one will be while running and I operate outside. I stop the mains ground at the variac and do not get it anywhere close to the TC. Everything at the TC that needs ground uses RF ground. However, RF grounding of the NST has both pros and cons. PRO: if anything bad gets on the NST output, it is more likely that it will hit the NST chassis before getting to the NST primary and the current will be returned to the base of the coil (RF ground) and not go thru the house wiring. This connection may also help keep RF currents off the mains ground. CON: some believe this will stress the primary insulation more since any voltage difference between RF ground and mains ground will present itself between the NST core and primary winding and across the primary insulator bushing coming out of the NST chassis. I believe the primary is wound on a plastic bobbin and as such is fairly insulated from the core and the primary bushings should be good for several thousand volts. Anyway, a good RF ground connection to earth will probably keep the voltage difference between the two ground under control. Another con might be more RF on the line (hot and neutral). This, however, can be addressed with a line filter.

Gerry R.


Original poster: "Neal Namowicz" <mr_neal@xxxxxxxxxxxx>

The more and more I read your questions and answers, the more I realize how little I know! But, anyway, here's another question for y'all, that I've seen varying answers to. When using an NST, where should I ground it to? Or should I ground it at all? At the moment, mine is grounded to the house ground, instead of RF ground. Then I've read somewhere where someone said NOT to ground the NST's. FWIW, I'm told by my family that the TV upstairs barely shows any interference at all when the coil's running, but would grounding it to the RF ground eliminate even more of it? Your suggestions, as always, would be greatly appreciated.

Neal.