Re: coax braid vs. solid conductor, was coil pictures andobservations

-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Saturday, July 31, 1999 7:08 AM
Subject: Re: coax braid vs. solid conductor, was coil pictures

>Original Poster: FutureT-at-aol-dot-com
>In a message dated 99-07-30 06:11:07 EDT, you write:
>> IMHO, braid sucks in any RF application, no matter what the wire
>> coating. The reason is not the quality of the conductor but that the
>> skin effect forces the current to hop strands, and anyone who
>> services electronics for a living will know how reliable connections
>> are.
>> Malcolm >>
>Hi Malcolm,
>I remember you did those braid vs. other conductor tests.  In your
>opinion, how much spark length would be lost (ballbark) by using
>coax braid instead of copper tubing or solid wire of the same diameter
>in a typical TC that gave a 36" spark, and used about 15 turns on
>the primary?  Figure 120 bps sync operation if it makes any difference.
>John Freau
Hi All,
I Tried a comparison test a month ago after finishing my new .25" copper
tube primary. I had been using a tightly wound primary made with RG-59  coax
in the past. When I switched to the new primary I noticed a dramatic
increase in performance. I had to check this out further and find out why.
Naturally, since copper tubing has no insulation I had wound it with .25" of
space in between turns. I needed to know if my previous losses were caused
by the conductor itself or inter turn capacitance. Dielectric breakdown
would make itself well known so I tossed out that possibility.
I wound yet another primary out of RG-59, this time with .25" space between
turns (I approximately took the insulation thickness into account). I
noticed that the tune point was identical to the copper tubing, and greatest
of all, the streamer length was identical. This means that the losses with
my first primary was not due to the cable at all, but was probably due to
capacitance between turns or possibly proximity effect. When you have
insulated cable it is very tempting to tightly wind it because it makes for
a very compact design, but the output will suffer for it. Just for the
record, all of my primaries are of the flat design. The RG-59 is foam
dielectric with two shields(the conductor in this case) One is stranded
tinned copper braid and the inner shield is aluminum foil. The center
conductor is copper wire and I just let this float, the electrons don't use
it so I don't bother to either. I have now switched to .018uf mica cap, and
9/60 neon. My spark length is 27.5". Next I will put my ball gaps in place
of the RQ and see if there is any difference.