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Re: H/D Ratios

Subject:  Re: H/D Ratios
  Date:  Wed, 28 May 1997 17:03:53 -0600
  From: "DR.RESONANCE" <DR.RESONANCE-at-next-wave-dot-net>
    To: "Tesla List" <tesla-at-pupman-dot-com>


To: John C.

Hi John:

We usually calculate our design lengths to 88% of the actual 1/4 wave
length.  This seems to work out well for most coils running in the 3-8
kva
range.  We sort of reversed engineering our actual physical measurements
to
obtain this value.  We use 88% of the calculated 1/4 wave calculated
wire
length for the design.  This of course assumes a toroid is being used
that
is in line with the design parameters, ie, a 20 inch toroid on a 12 inch
dia. coilform and a 34 in. toroid on a 18-20 in. coilform.

We're up and running back in Wisconsin --- and freezing!  Yikes -- highs
of
only 55 degrees in late May -- what a nasty spring.

Stay warm in SD -- regards,

DR.RESONANCE-at-next-wave-dot-net


----------
> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-poodle.pupman-dot-com
> Subject: Re: H/D Ratios
> Date: Tuesday,May 27,1997 7:17 AM
> 
> Subject:  Re: H/D Ratios
>   Date:   Tue, 27 May 1997 06:32:58 +0000
>   From:   "John H. Couture" <couturejh-at-worldnet.att-dot-net>
>     To:   Tesla List <tesla-at-pupman-dot-com>
> 
> 
> At 05:55 AM 5/23/97 +0000, you wrote:
> >Subject:       Re: H/D Ratios
> >       Date:   Thu, 22 May 1997 08:46:30 +1200
> >       From:   "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
> >Organization:  Wellington Polytechnic, NZ
> >         To:   tesla-at-pupman-dot-com
> >
> >
> >Dear List,
> >           Please indulge me once again :)
> >
> >> I have seen several references to a physical 1/4 wavelength of wire
> >> being used to wind a secondary. What is the 1/4 wave length based on?
> >> Is it free space or based on some velocity factor? Is there some magic
> >> to be had by striving for this.
> >> 
> >> Based on no facts at all my next secondary will have a H/D ratio of
PI.
> >> It just seems right.
> >
> >Love it :)
> >     The quarter wavelength thing: In the distributed resonator, no 
> >matter what the length of wire, the profile is 1/4 wavelength at 
> >resonance. Well, that is _strictly_ true for no top load (or nearly 
> >so because like a standard antenna, there is an end capacitance 
> >effect that requires the physical length of the straight wire to be 
> >somewhat shorter than the free-space length). As soon as one adds a 
> >topload, the antenna/coil will resonate at a lower frequency because 
> >of the additional capacitance. That makes the structure shorter than
> >90 degrees electrically at its resonant frequency. The lower the L/C 
> >ratio, the more the electrical length trends towards zero degrees.
>      I'd better stop there. I think I may have started writing a book.
> 
> ----------------------------  Big snip
> >
> >Other comments welcome,
> >Malcolm
> 
> ------------------------------------------------------------------
> 
>   Malcolm -
> 
>   I agree with you that the 1/4 wavelengths and antenna concepts for
> Tesla
> coils does not stand up to what is found with real world coils. In the
> TC
> data I have collected the secondaries of almost all of the coils do not
> conform to the 1/4 wavelength theory either for the actual or electrical
> wavelength.
> 
>   This makes sense because the TC is a resonant air core transformer
> with a
> copacitance load and 1/4 wavelengths are not important. The TC is a dual
> RCL
> circuit where both primary and secondary circuits  must have the same
> resonant frequencies  for optimum output. TCs operate the same as
> standard
> resonant transformers and helical antenna concepts are not involved.
> 
>   The fact that the maximum voltage is next to the top capacitance is
> typical for a transformer when the voltage is measured across the
> secondary
> coil with one end grounded. This is why any size capacitive topload can
> be
> used as long as the dual RCL circuits are in tune.
> 
>   Tesla always said his TC invention was not for Hertzian waves but for
> currents. Helical antennas, etc. that are Hertzian wave devices are not
> involved. I now think that the VSWR is also not involved because there
> is no
> transmission line to couple the coil and capacitor load. Note that an
> antenna is a resistive load at the end of an RF transmission line. This
> is
> not the TC type of circuit.
> 
>   The H/D ratio concept has only to do with maximum inductance and
> little to
> do with transformer operation. However, higher inductance does mean more
> output with resonant tranformers.
> 
>   John Couture