Question on Ceiling Height/Material

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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