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Wire length,resonance, and Q
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From: Greg Leyh [SMTP:lod-at-pacbell-dot-net]
Sent: Tuesday, May 26, 1998 2:22 PM
To: Tesla List
Subject: Re: Wire length,resonance, and Q
> > I think most would agree that the 1/4 wave formula is not absolute for operation,
> > but, just as Tesla used the 1/4 wave calculation as a guide, when answering
> > questions for new coilers who are looking for the number of turns for a
> > secondary, I would suggest the 1/4 wave calculation, as it does put them right
> > into the operational ballpark. Would others agree on this?
> > -Bart
>
> You can do *much* better by using Medhurst's Cself and Wheeler's
> Lself. I think those old equations should be thrown away forever.
[snip]
> -Malcolm
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