RE: Quick toriod question...

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Gary.Lau-at-compaq-dot-com>

HI Richie:

That's very strange!  I would have expected any arcing between tape layers
to occur at the same time, same spectrum (same channel ;-) as the streamers,
with no net difference in TVI.  Were the two toroids close enough in size
that tuning differences can be discounted?  Just how poor was the tape
overlap before you flattened it out?  It's interesting how just like with
secondary losses, CW coils can reveal otherwise unknown toroid losses.  

Regards, Gary Lau
Waltham, MA USA

 -----Original Message-----
From: 	Tesla list [mailto:tesla-at-pupman-dot-com] 
Sent:	Thursday, December 21, 2000 7:34 PM
To:	tesla-at-pupman-dot-com
Subject:	RE: Quick toriod question...

Original poster: "R.E.Burnett by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<R.E.Burnett-at-newcastle.ac.uk>


Hi Gary & all,

An interesting point,  about poor connections in the toroid.  Here's
something you might find interesting:

My Solid state coil produced no TVI at all with a spun toroid fitted. 
However, when I replaced the spun toroid with a plastic one coated with
many layers of overlapping foil tape,  I got terrible TVI at first !

Running the coil in complete darkness revealed a line of arcing between
two overlapping pieces of Aluminum duct-tape,  and some local heating. 
When I flattened out all of the foil tape to improve the contact,  all of
the TVI dissapeared again.

The arcing internal to the toroid did not impair the streamer length
noticeably,  but it obviously diverted some of the input power into UHF
radiation !

I can produce a similar effect by placing two metal objects near to the
running TC.  If they are very close, (like 0.010" or so) they will arc
and this produces a lot of snow on the TV.

_Unfortunately_  replacing the foil toroid on my classic TC did nothing
to ease the TVI which that beast produces.  Oh well it was worth a try :-(

							Cheers,

							-Richie Burnett,

> Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<Gary.Lau-at-compaq-dot-com>
> 
> This thread raises another question in my mind.  It appears that most
> home-made toroids use aluminum foil tape as the conductive surface.  But
> even though the individual strips overlap each other, the adhesive is not
> conductive, and an Ohm meter will indicate that they do not in most cases
> connect to each other.  Perhaps the thinking is that when we're looking at
> 100's of kV, a thin layer of goo is probably not going to put up much of a
> fight before breaking down.  
> 
> But even so, I've always wondered whether this resistance between each
tape
> segment might have a significant effect on performance when a streamer
wants
> to suck the energy in the toroid off in a hurry.  If each "plate" in the
> toroid-capacitor has a resistor and a spark gap connecting it to the disk
> terminal, that can't be good.
<snip> 
> Back to my question - I'm wondering, am I the only person to worry about
> connections between the tape strips?  How do others deal with this?
> 
> Gary Lau
> Waltham, MA USA