Re: Tapered Secondary Coil

To: tesla-at-pupman-dot-com
Subject: Re: Tapered Secondary Coil
From: Richard Hull <hullr-at-whitlock-dot-com>
Date: Tue, 28 Mar 2000 21:53:48 -0800
Tesla List wrote:
> 
> > > Subject: Tapered Secondary Coil
> > Subject: Re: Tapered Secondary Coil
> > > Subject: Tapered Secondary Coil
> 
> >From sgreiner-at-mail.wwnet-dot-com Thu Dec  5 22:59:16 1996
> Date: Thu, 05 Dec 1996 15:17:29 -0800
> From: Skip Greiner <sgreiner-at-mail.wwnet-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: Tapered Secondary Coil
> 
> Tesla List wrote:
> >
> > > Subject: Tapered Secondary Coil
> >
> > >From bert.hickman-at-aquila-dot-comSat Nov 23 20:04:43 1996
> > Date: Sat, 23 Nov 1996 09:35:07 -0800
> > From: Bert Hickman <bert.hickman-at-aquila-dot-com>
> > To: tesla-at-pupman-dot-com
> > Subject: Re: Tapered Secondary Coil
> >
> > Tesla List wrote:
> > >
> > > >From scottb-at-aca.caFri Nov 22 20:30:34 1996
> > > Date: Fri, 22 Nov 1996 15:37:04 -0500
> > > From: scottb-at-aca.ca
> > > To: tesla-at-pupman-dot-com
> > > Subject: Tapered Secondary Coil
> > >
> > > I have seen some secondaries that are tapered, and some that are not.  What
> > > (mathematically) is the difference, and what are the effects??
> > >
> > > /sb
> >
> > Scott,
> >
> > A tapered secondary (with the larger diameter at the bottom) has
> > decreasing inductance per turn as you go higher up the coil. When used
> > as a resonator with little or no top-loading (small discharge terminal),
> > it exhibits a less well-defined resonant frequency (i.e., lower Q) than
> > a constant diameter resonator. The characteristic impedance of a tapered
> > resonator also varies with height, being higher Z at the botttom, and
> > lower at the top. A tapered resonator also has substantially less
> > "lumped" inductance than one with constant diameter (equal to the base).
> >
> > A tapered resonator will see less overall resonant rise than a
> > constant-diameter resonator of the same height and base-diameter.
> > However, it should also be less sensitive to detuning from stray
> > capacitance. Because most of the inductance is concentrated in the lower
> > half, the voltage stress at the bottom portion is greater than for a
> > constant diameter coil.  Addition of significant top-loading capacitance
> > should sharpen the tune somewhat, but the resonator will retain its
> > distributed parameter (transmission-line) characteristics to a greater
> > degree than a constant diameter resonator.
> >
> > There appears to be no marked performance advantage in using a tapered
> > resonator versus a standard helix in a 2-coil system. However, it sure
> > looks different...
> >
> > Safe coilin' to you!
> >
> > -- Bert --
> 
> Bert and all
> 
> Has anyone tried to build a tapered resonator and run it upside down,
> ie., drive the thing at the small end. Couple of interesting
> observations: the top of the coil is self shielding, no toroid is
> necessary, the distributed parameters (inductance) may enhance the
> voltage rise.
> 
> I will build one if someone can give me a reasonable way to do it.
> 
> Skip


Skip,

I have wound a couple of conical coils (tapered) and inverted them as 
well.  The inversion grossly reduces the coupling in a standard primary. 
(All the inductance and wire is up top!).  In general, I found that 
normal conical coils are somewhat disappointing.  The self shielding 
aspect of the inverted resonator is quite novel, but the prmary would 
have to be modified to achieve good results.

Richard Hull, TCBOR