From: boris petkovic
Date: Mon, 11 Sep 2000 11:05:25 -0700 (PDT)
Subject: Re: [TSSP] Mystery of the missing loss
Hi All, > My antennae shot up when I read this: > > > >3.)Possibly extra high dielectric loss in coil > form > > > (unlikely here I think) > > > > Now this I can NOT rule out! The secondary seemed > to have much higher loss > > at low frequencies than at high!! ----- ?? It would be first such case Iv heard of. Probably the secondary just seemed that way. ----- Using my vacuum > cap (which actually > > showed a loss higher than my super cap!) I could > clearly see that higher > > frequencies had higher loss. ----- This is how it should be.. ----- > http://216.160.168.190/TeslaCoils/Misc/PaulNich/BRacvF.gif > > > > Basically, it says something is getting very lossy > very fast as frequency > > increases. I have no idea what, ----- Everything becomes more lossy as freq. increases. ----- > > > This secondary is a 1/8 inch thick cardboard > impregnated with paraffin wax > > "sonotube" used for circular concrete forms. This > wire may have had an > > oxide layer at the surface before it was coated. > The vacuum cap is > > probably more lossy at low capacitance than high > Maybe the polyurethane > > coating is doing something... The list goes on... > but I seem to be > > getting super high loss as frequency increases. > > My one *really* bad secondary (which I actually > threw away) > was wound on sonotube with the tar layer removed. > That coil > was spacewound to boot! > I don't think the polyurethane is the culprit. > More > likely the paper form. Wax is possibly also not the > best. > Remember those old transformers from the forties? > which went > o/c in the sixties? the rotted copper inside > complete with > verdigris (sp?)? I never decided whether they were > trapping > moisture inside or admitting it. > > > >4.)EM Coupling of secondary with enviroment and > losses > > >outside a coil structure. > > > > I have done such tests a number of times in a > number of places and gotten > > similar results. I don't have an oxygen free > silver plated room coated > > with a gold anti-oxidation layer or anything, but > the room is not all that > > unusual... I would guess the previous option > three... > > I think that is a good bet. The room does make > difference once > Q's get beyond a hundred or so but not to that > extent (say six > foot clearance all round). ----- I think I will agree.Terry is having problems in reaching Q beyond 80,and higher res.freq. Qs are just terrible low for the coil. Coil form dielectric losses turn out to be the solution of the riddle in first place -the dominant losser (althought ,I have no idea why particular coil form is so lossy here). Time to think about whole thing all over again. -- > > I have played with some modelling and I think the > "room" is far enough away > > that it should not be a factor. It is raining now > so outside is not an > > option. There are a number of things in the Rac > loop but the coil form > > really does seem lossy to me... > I changed my mind ,and now have opinion that you'll never force your coil to have Q > 120 .Regardless of superior enviroment,grounding connections,ideal earth -coil loops or anything. Regards, Boris __________________________________________________ Do You Yahoo!? Yahoo! Mail - Free email you can access from anywhere! http://mail.yahoo.com/
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.