Re: Any ideas on this proposition?

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

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-uswest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
> 
> Original poster: "Dr. Duncan Cadd by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <dunckx-at-freeuk-dot-com>
> 
> Hi John, Richie, Alex, et al!
> 
> >An interesting circuit
> >for a tube coil is one recommended by DC Cox.  This involves using
> >a primary with many turns, and tapping it at some point.  Then
> >another wire is connected to the primary at some different tap point
> >and the other end of the wire feeds the base of a resonator.  This
> >method eliminates the need for electromagnetic coupling, and can
> >match a wide range of impedances.  The tap points are moved
> >around until the best tap points are found.  I've tried this method,
> >and did obtain about 10% longer sparks.  The resonator is
> >connected to the primary circuit though, so I guess it may be
> >more dangerous.  When the sparks hit a ground, they seemed
> >to be sinking more current than normal.
> >
> >Any comments on such a circuit?
> >
> >John
> 
> I've copies of this circuit in books on spark transmitters.
> Effectively a sort of rf auto-transformer.  It obviously worked well
> in the days of spark.  No doubt it would work on conventional spark
> coils too (but see comment later).

	This is an example of the kind of "direct-coupled" circuits which were
used before people became more concerned with spurious signals and
interference.  I suspect that it has no merit over the
inductively-coupled circuit, which can also be impedance-matched by
adjusting coupling and tuning.

Ed