Re: Capacitor "tap" in Primary?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
> 
> Original poster: "Jolyon Vater Cox by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>
> 
> Is it possible to get an autotransformer-like step up on a primary of a
> spark-gap TC using a capacitor tap -in a manner  similar to that  exhabited
> by the tuned circuit of  a Colpitts oscillator (but without the amplifier
> and feedback)?

A capacitor in parallel with the gap would be immediately discharged
when
the gap fires, and have little effect while the gap is conducting.

It seems possible, however, to feed a "capacitive transformer" (a
grounded
coil in parallel with two capacitors in series) through the tap between
the capacitors with a signal at the resonance frequency of the system
and 
get high voltage at the top of the coil. It would be curious to see if
this
works with the upper capacitor being a distributed capacitor between the
coil and a terminal above it and a plate below (as a ground plane) 
connected to the lower, grounded, capacitor. 
 
> By the way, how does the "Poulsen Principle" work
> only it seems strange that adding a capacitor directly across a spark gap
> would would do anything to make it run cooler. Are there any good references
> to the technique and does anyone know how it works?  Could it be that the 2
> nF cap act to remove HF transients that would otherwise heat the gap -a bit
> like a snubber across a TRIAC or a Zobel network across a loudspeaker, by
> any chance?

I have never heard about this, but a capacitor across the gap may serve
to quickly heat up the air in the gap, reducing losses during the 
oscillations that follow, may reduce spurious RF being irradiated, and
may cause the gap to quench more easily when the energy in the primary
tank drops. This last function may be really useful.

Antonio Carlos M. de Queiroz