Re: Ground box

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

Original poster: "davep by way of Terry Fritz <twftesla-at-uswest-dot-net>" <davep-at-quik-dot-com>

Tesla list wrote:
 
> Original poster: "Ray Robidoux by way of Terry Fritz
><twftesla-at-uswest-dot-net>" <robidoux-at-basystems-dot-com>

> Hi Malcolm,
 
> Thanks for your explanation, but I am still confused.

	Likewise.  Runs counter to my experience, but I'll
	not debate the observations.

> My experience does not agree. I am using an 8" piece of
> braid right now in my primary. It is the wire that
> forms the connection for my tap on the primary down
> to the SG. I have touch this many times, while tuning
> for example, and have found this piece of braid to be
> STONE COLD. I have NEVER found this braid to be even
> the slightest bit warm, but ALWAYS as I have said above
> "stone cold".
 
> Also your explanation of how current, "has to hop from
> one strand to another", makes me wonder about stranded
> wire in general. In a standed wire don't those strands
> have to "duck and dive under each other along the length",
> as well.

	Not usually.  Take the insulation off a piece, carefully.
	Have a careful look.  The strands spiral predictably
	and in a controlled fashion around each other.  They
	do not duck & dive.
	(use a large ga wire, or a magnifier on small gauge).

> That would seem to put stranded wire in the same
> category as braid.

	cf above.

	An exception (i think) is proper litz wire....)
> > -----Original Message-----
> > From: Tesla list [mailto:tesla-at-pupman-dot-com]
> > Sent: Sunday, April 08, 2001 5:54 PM
> > To: tesla-at-pupman-dot-com
> > Subject: RE: Ground box

> > Original poster: "Malcolm Watts by way of Terry Fritz
> > <twftesla-at-uswest-dot-net>" <m.j.watts-at-massey.ac.nz>

> > Hi Ray,
> >          I can help explain this braidophobia very succinctly:

> > On 6 Apr 01, at 12:18, Tesla list wrote:

> > > Original poster: "Ray Robidoux by way of Terry Fritz
> > > <twftesla-at-uswest-dot-net>" <robidoux-at-basystems-dot-com>

> > > Hi All,

> > > I am very confused as to why this list has such a dislike
> > > for braid. I have seen many comments like this against the
> > > use of braid in TC work. My experience with braid is
> > > that for the same amount of copper (and 90+% optical
> > > coverage) the braid is an order of magnitude better than
> > > solid wire at conducting RF energy. The reason for this
> > > is exactly why we use refer tubing in the primary of a
> > > TC. It is the skin effect, the fact that the center of
> > > a conductor is useless in conducting RF currents. Therefore
> > > you want to increase surface area in the conductor to
> > > decrease current density. When using braid the most
> > > important feature to examine is the so called
> > > "optical coverage". This is the amount of light blocked by
> > > the strands of braided wire (strand density). Braid comes
> > > in all sorts of optical coverage(OC), from 10-% to 90+%. One
> > > can imagine that 20% OC braid is useless, and in fact is
> > > typically used in conjunction with aluminum foil to make it's
> > > shielding and conducting properties better. I would not use
> > > any braid with less than say 90% OC. If you look at the pics
> > > that Terry has shown, which is going to be the better conductor,
> > > I find it hard to believe its the center wire which has maybe
> > > 1/10th the amount surface area than the braid. I would like
> > > to hear others thoughts on this matter.

> > Unfortunately, it is precisely the skin effect that works against
> > braid. There can be no doubt about how poor it is - I have measured
> > it in a carefully crafted expt. I then went and proved the point by
> > running a high current primary with a foot of it included. It got
> > hotter than the brass blocks holding the gap electrodes.

	How big were the blocks?
	Were they cooled by the air from gap (if a rotary?)?

> >       The strands duck and dive under each other along the length.
> > Since skin effect is trying to keep current near the outer surface of
> > the braid, the current has to hop from one strand to another at every
> > point. Result: to RF, braid is like including thousands of
> > connections in series, and contact connections are generally less
> > than perfect. Braid was the standout worst performer in my tests by a
> > country mile.

> > Malcolm

	best
	dwp