TSSP: List Archives

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

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Maintainer Paul Nicholson, paul@abelian.demon.co.uk.