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Re: Tapered Secondary Coil
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 haven't built one, but you've got my curiosity aroused. I'd suspect
you'd still want to use a toroid to prevent premature breakout from the
top of the coil. The inductive coupling from the primary to the smaller
base of the coil may also be significantly poorer, but might be
compensated for by using a matching inverse conical primary. It'd be
interesting to see if there were any unsuspected advantages!
I'd make a conical coilform template out of posterboard, and once I was
satisfied with the rolled up results, make the same out of thin (30 mil)
LDPE sheet material, and once rolled into a cone, secure it with small
strips of insulating tape. Obviously, you're going to have to figure out
some way to rigidly mount the small base end to hold it in the top-heavy
position...
Good Luck, and safe, inverted, coilin' to ya, Skip!!
-- Bert --