Re: coax braid vs. solid conductor, was coil pictures ando
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Tuesday, August 03, 1999 6:37 AM
Subject: Re: coax braid vs. solid conductor, was coil pictures ando
>Original Poster: "Malcolm Watts" <malcolm.watts-at-wnp.ac.nz>
> I don't think capacitance between primary turns could
>be a culprit because capacitance is a lossless element.
I really wasn't thinking "lossy" as being resistive. I was thinking more
along the lines of the capacitance bypassing the RF energy across the
primary and acting as an RF shunt. I think Terry's explanation about the
coupling coefficients is also a possibility.
>The question: if you wound a new primary with spacing between turns,
>there must have been a difference in the number of turns if it was to
>tune to the same frequency as the old primary. Did you take such
>differences into account?
Yes, the old primary tuned at 10 turns, and the new one at 12.
> I don't think there should be a huge difference between braid
>and copper as far as output goes. What I do think is that it is
>desirable to minimize circuit losses as far as possible (good
>engineering practice) and if it is possible to eliminate heating in
>some component, why not? The amount of heating in braid or anything
>else is integrated over time as a function of its ability to lose
>heat (amongst other things) so the heating is cumulative and not that
>horrendous over a short period. Braid does measurably reduce the Q of
>a good circuit. In the primary, one has the gap and if some added
>resistance appears in the circuit, gap current will be a bit lower
>along with the corresponding VI gap loss (assuming V plateaus at a
>low voltage which curves I've seen suggest it does).
I guess I don't run a high enough power, or long enough runs to notice any
heating in the braid. I did notice heating in the primary of my little micro
Tesla coil (totally different project). In that one I am using 14 AWG wire
and encapsulated it in epoxy to make it behave because it was unsproinging
all over the place. I made the heating effect noticeable by trapping it with
the epoxy. I was surprised though because I am only running 5KV -at- 25
milliamps for that project. Should have used 12 awg dagnabbit!