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Re: Question on Ceiling Height/Material

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Jim,

At 11:23 AM 5/24/2006, you wrote:
Hello List Members,
I recently noticed that the ceiling height and material can make a significant difference in a coil's secondary frequency.

You bet!!  E-Tesla was sort of inspired by situations like this:


where it was hard to guess at the tuning, and ever harder to fiddle with it!!

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.

In general, even gypsum will present a sufficient boundary for HV RF. Probably not as good as steel and probably at a higher loss, but good enough. It is not so much a conductor, but a capacitor that will zero the voltage out trying to charge it at that point, but the results are the same.

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).

Yes. If you reduce the primary to secondary coupling, it will be less sensitive. But that might reduce the spark size too... Not sure...



Jim Zimmerschied