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Re: 3/4 wavelength secondaries

Tesla List wrote:
> 
> >From ed-at-alumni.caltech.eduTue Jul 30 22:26:56 1996
> Date: Tue, 30 Jul 1996 16:52:31 -0700 (PDT)
> From: "Edward V. Phillips" <ed-at-alumni.caltech.edu>
> To: tesla-at-pupman-dot-com
> Subject: Re: 3/4 wavelength secondaries
> 
> Question: Why the interest in free-space wirelength?
>         There have been a lot of listings here lately in
> which it appears that the author thinks there is something
> "magic" about having the coil operate near the free-space
> quarter-wave resonant frequency of the winding.  I can't see
> what difference this really makes, as long as the coil is
> excited at the correct resonant frequency as determined by
> self and lumped (top terminal) capacitance.  Am I missing
> something?
>         One other point.  Although I don't remember seeing
> it expressed explicitly, the effects of a top toroid are
> at least twofold:
> 1. The L/C ratio of the secondary is lowered, reducing its
> surge impedance and hence the loss of Q for a given power
> lost in discharge.  Seems to me this should increase the current
> when the discharge starts.
> 2. The breakdown voltage is increased, increasing the formation
> of the streamers which finally carry current when breakdown
> occurs.  In the case of one of my small coils, this effect takes
> seconds.
>         Any comments from the
>         "Richard's"
> or anyone else?
> Ed Phillips


Ed,

You are correct about the grossly reduced base impedance and the natural 
increased output current.  We are just stiffening up the source of 
voltage with a large toroid.  Also, as you stated Q generally drops with 
any terinal addition and always drops with really large toroids.

Streamer formation, that is, individual streamers, are always REDUCED 
with increasing toroid size.  As more energy is required per arc, a given 
energy input results in far fewer individual breakouts which are very 
violent and bright indicating a richness of arc channel current.  See my 
DC post.  The ion cloud response on small coils is rather fast and 
limited.  On really huge systems, the cloud takes some seconds to form 
and stabilize.  Tune shifts about a bit with the ion cloud and air 
currents, which, with very large systems, is always present by localized 
heating of the air by the arcs.

Richard Hull, TCBOR