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Okay, putting together my first OBIT coil (I know, usually the progression is OBIT, then NST, but not this time. *grin*), and I was wondering a couple of things. First, is a high-side filter (like a "Terry filter") necessary for protection of these transformers, as with NSTs? And then, should I put an EMI filter on the low side, or is the impedance of the transformer protection enough for the source line and other equipment connected thereunto?
Registered Member #690
Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616
An EMI filter is always a good idea, especially if you already have one. The coil will obviously work fine without it, but you may interfere with household items (more than usual).
As for the Terry filter, a transformer is a transformer whether it powered a neon sign or an oil burner igniter. Just windings on a core... The Terry filter is the proven best, but you could get by with some series filter chokes, and filter caps across the poles and. center tap.
See, as far as the OBIT+Terry filter goes, I wasn't sure how necessary it was. Even from some posts Terry himself has made both here and on pupman, I got the impression that NST secondaries are uniquely sensitive to RF -- the the extent that in one of his posts he recommended against using it on any type of transformer other than an NST.
Re: EMI filter . . . then that's definitely going in. In fact, I'll probably rig up a power filter/ground tie-in box so that I can have my mains ground tied to a grounding post as well . . . what fun is life if you don't have a couple of copper grounding rods in your back yard? *grin* (As well, my ca. 1917 house has rather poor grounding . . . )
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
I don't think filtering is neccessary for an OBIT.
VERY important is to have a safety spark gap - with nothing else connected to the secondary set the gap to just fire, OR make sure the main gap never gets too big.
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OBIT protection and line filtering
