[Prev][Next][Index][Thread]
Wire length,resonance, and Q
----------
From: Barton B. Anderson [SMTP:mopar-at-uswest-dot-net]
Sent: Wednesday, May 27, 1998 2:08 AM
To: Tesla List
Subject: Re: Wire length,resonance, and Q
Greg, Malcolm, All,
Tesla List wrote:
> <snip>You can do *much* better by using Medhurst's Cself and Wheeler's
> > Lself. I think those old equations should be thrown away forever.
> > -Malcolm
>
> <snip>I agree with Malcolm that the old 1/4 wave treatment of TC's should
> be totally discarded. There is no apparent correlation between wire
> length and F res -- It's only a happy accident that there is roughly
> a 1/4 wave of wire in the more popular TC secondary sizes.
> The use of Medhurst's Cself and Wheeler's Lself is more accurate.
>
> Actual current waveform measurements show that the operation of the
> secondary coil much more closely resembles that of a lumped-element,
> series LC resonant circuit.
>
> A beginner might end up in the ballpark using the old 1/4 wave idea,
> but why perpetuate an incorrect model that sort of works?
> When I was laying out my first coil, I would have greatly appreciated
> knowing that the 1/4 wave treatment of TC's was bunk!
>
> -GL
> www.lod-dot-org
> <snip> Don't see why. If yu feed in a lump of energy and that energy is
> mostly concentrated in Ctop at some stage then the old 0.5CV^2
> applies. I loved Greg Leyh's explanation of why it *should* apply,
> namely that the V^2 term is highest at the top. I think calculating
> Vout based on no terminal is academic unless one runs with no Ctop
> but then how well can you do if you are lacking ROC at the top?
> What thinks anyone?
>
> Malcolm
>
Ok, there's seems to be a lot of agreement on this. This is good. When I first began my
coil build (actually second time - I hate to count the first), I used formula's for 1/4
wave and had wound my secondary accordingly, I then went through a learning curve and
came across Medhurst and Wheelers equations, applying these to my Ctop, primary, and tank
cap. It's been said before there are a million different ways to get to the same point. I
must have been one of those that actually grouped them all into one (grin). I guess I
never realized I was removing the 1/4 wave out of circuit and didn't correlate the
seperation. I was under the assumption that Wheeler's equation was getting to the same
point of wire length resonance from a different path. That's what I get for assuming.
I would agree with you Greg, that it is rediculous to perpetuate an incorrect model that
sort of works. Time to go back and re-cap on lumped series and parallel LC resonant
circuits.
Thanks to EVERYONE for this clarification,
Bart