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Question on Ceiling Height/Material

Original poster: "James Zimmerschied" <zimtesla@xxxxxxx>

Hello List Members,
I recently noticed that the ceiling height and material can make a significant difference in a coil's secondary frequency.

Case in point - I was trying to get my DF-DRSSTC working. I couldn't get it to break out properly and it was drawing too much current. I took the coil over to a friend's house and it was working well - got 18" arcs to a ground rod - with no change in the coil configuration. What was the difference? My friend said his shop which has a flat metal roof, suppresses the operating frequency of his coils. When he moves them outdoors, they have to be retuned. When I was trying to run this coil before, I was in my garage which has no "ceiling" only open rafters up to the roof.

In playing with parameters in JAVATC, I see a noticeable change between an 8 ft ceiling and a 12 foot ceiling. I don't see anything in the program that inputs the material type for the ceiling. I would think a non-conductor like gypsum wallboard would have less effect than a flat steel roof. Maybe Bart could shed some light here.

The bottom line for me is to accurately model the room envelop when running a TC modeling program. Also, if you relocate the coil - say from in the garage to out on the drive way - expect to have to retune (possibly reconfigure).

Jim Zimmerschied