Re: braided secondaries???

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

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

Hmm, Litz wire...

It is the old stuff I believe...
Its non-plastic enamel(the real stuff) with what appears to be REALLY dusty
silk or some blend....  Thin stuff.

I dont know what condition the wire is in on the rest of the spool, but the
1st ten feet look ok to me.
 I think that cause I have it, might as well see what happens with a small
secondary with the wire...

Thanks Guys!

hmmm, I'd better start using a real name..
:)
Erik(The artist formerly known as S....)
----------------------------------------------
Original Message
From: "Tesla list"<tesla-at-pupman-dot-com>
Subject: Re: braided secondaries???
Date: Tue, 20 Mar 2001 17:28:17 -0700

>Original poster: "Dr. Duncan Cadd by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <dunckx-at-freeuk-dot-com>
>
>Hi S, Ray!
>
>
>>Original poster: "Ray von Postel by way of Terry Fritz
><twftesla-at-uswest-dot-net>" <vonpostel-at-prodigy-dot-net>
>>
>>S:
>>
>>What you have is "Litzendraht wire"  also called "Litz wire".  It is
>>used in coils operating at low  radio frequencies to
>>minimize the skin effect and thus the  r. f.. resistance.
>
>With fine enough (50swg / 0,01mm) wire, it is/was used to as high as
>3Mc/s.  At these higher frequencies, the success depends to a large
>extent on the even-ness of the braiding and how well the individual
>strands are insulated from each other, a bit of space between each
>wire becomes important.  Often the strands were enamelled and fabric
>covered before being braided together in order to get that bit of
>extra space.
>
>>I have seen it as much as 2 inches in diameter in the coils of
>>transmitters and in small sizes as the wire
>>used to wind low frequency i.f.. (intermediate frequency) coils in
>radio
>>receivers.
>
>There's a photo from the Rugby "wireless" station in the early 1920s
>of a big, low loss transmitting coil using what I take to be very
>thick litz cable as per Ray's description on my page at:
>
>http://home.freeuk-dot-net/dunckx/wireless/maxpower2/maxpower2.html
>
>The station still exists but I doubt they have anything like this
>there any more.  I could be wrong though, they have a 60kc/s
>transmitter plus massive masts/aerial system for the standard time
>signal from the National Physical Laboratory and it's just possible
>they might still have a big LF litz coil like this one for that very
>purpose.
>
>>I have no idea where you could get a current price for Litz wire,
>>but 30 years ago it was as much as 10 times the cost of
>>enameled wire.
>
>A lot more now, as the cost of fabric (real or artificial silk)
>covering has increased dramatically and few firms have the machinery
>to do it; typically one ounce costs around 10 UK pounds, so if you
>have five lbs of it, you have a real find :-)  A few hundred $$$ worth
>at a guess.  You might make a bit by selling it at a hamfest!  I'm
>assuming that S's litz is fabric as well as "enamel" insulated.
>
>>You will find it hard to solder because each wire end has to be
>cleaned.  There
>>is a procedure for that in some old editions of "Chemistry and
>>Physic's HandBook"  published by the Chemical Rubber Publishing Co.
>Your
>>local library should have a copy.
>
>
>For the skin effect to be reduced, each individual wire of the litz is
>insulated from its neighbours and you have to get that insulation off
>before you can solder it, a real pain when it's real enamel.  In my
>Father's day, you could either heat it to red heat in a flame
>(difficult without melting the wires clean through if they were thin)
>and plunge into alcohol (difficult without starting a fire because
>thin wires don't hold heat very long and so the flame has to be
>perilously close to the alcohol ;-) or you could take a razor blade
>and carefully scrape the enamel off (difficult, and a real pain if the
>litz contains dozens of individual strands, but the way Dad did it!)
>Difficult all round basically.
>
>These days you probably don't need to bother with all this palaver.
>The litz I bought a few years back was insulated with modern
>solderable "enamel" i.e. plastic and I expect if your wire is of
>recent manufacture, all you will need is a good, hot soldering iron
>and some flux-cored solder.  Have good ventilation when doing this as
>the fumes from decomposing polyurethane (isocyanates) are nasty.
>
><snip>
>
>I would guess that a spark-driven Tesla coil will see little
>improvement from litz (my baby coil of ~15W didn't seem to notice the
>difference though YMMV) since the secondary Q is of relatively little
>importance.  A CW coil is more likely to benefit as Q really does
>matter here, the higher the better.  It would be an interesting (and
>normally very expensive!) experiment to do.
>
>Dunckx
>
>
>
>

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