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Re: TWO STAGE COILS?



> Ok. I found schematics of the high-power Marconi transmitters in some
> old books. The best description is in a book by Fleming, that says
> that the system was his idea, and mentions several patents. The
> schematic shows: An alternator (G) in series with two inductances (L)
> and the primary of a step-up transformer. Keying of the transmitter is
> done by bypassing one of the inductances with a switch (S). The
> secondary of this transformer is in parallel with a first spark gap,
> and in parallel with the gap is a series connection of a capacitor (C1)
> and the primary of a first Tesla transformer. The secondary of this
> transformer is in parallel with a second gap, and in parallel with
> this second gap is a series connection of another capacitor (C2) and
> the primary of a second Tesla transformer. The secondary goes to
> the antenna and to ground. By Fleming's text, the first part is
> exactly a conventional AC-powered Tesla coil with inductive ballast
> on the primary of the high-voltage power transformer and resonant
> charging of the first primary capacitor. The book shows also, in
> the same picture, a schematic with only one Tesla transformer.
> The texts don't explain why two Tesla circuits in cascade (or I
> didn't see where). Maybe the patents say something.

	Does Fleming say anything about the resonant frequencies of the two
circuits?  Your description fits what I have here exactly, including no
mention of the relative resonant frequencies of the two separate
circuits.  Can't see any purpose, but those fellows were smart and
educated, and must have had something in mind.  Wonder if the patents
(British?) are available for study.  Anyhow, can see absolutely no
advantage of this arrangement for "normal" TC usage - big sparks and no
concern about the purity of the waveform.

> Other books show the same schematic, but add capacitors (Cg) in series
> with both sides of the secondary of the power transformer, as
> "guard capacitors" that have the function of avoiding the formation
> of a low-frequency arc in the first gap. Interesting idea. Ascii
> art drawing:

	Seems to me that those capacitors would cancel some of the reactance of
the primary ballast inductor, and thus be "counter productive".

Thanks for the discussion.

Ed