Re: SSTC As a transmitter.

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

Original poster: "Gary Peterson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <glpeterson-at-tfcbooks-dot-com>

> He didn't have a "local power supply" in the patent diagrams he
> published.

Some of the best receiver circuits are found in the COLORADO SPRINGS NOTES.
In fact Tesla considered or investigated at least 125 different variations
of receiver design while in C/S.  He included a battery along with a
variable resistance in those circuits which used coherers, so that a small
DC bias voltage could be placed across the device--an antenna and ground was
also connected.  In operation the bias voltage would be adjusted to a point
just below the coherer's breakdown voltage.   When so strained a small
increase in voltage resulting from an incoming signal would result in
coherence and the increased current flow would operate a small relay, which
also required a battery.  In some of his receivers he would also mix the
output of a local oscillator to create an audible tone in a telephone
earpiece.  It can be argued this anticipates certain aspects of the
heterodyne receiver.  He designed a small isocronous electromechanical
oscillator that was used this purpose.

The circuit diagram of one of Tesla's regenerative-type receivers can be
viewed at www.tfcbooks-dot-com/images/articles/tws5.1.gif.

> > > August 3 he shows a number of receiver arrangements in which RF
current is
> > > fed back from the secondary side of a resonant transformer to a
coherer
> > > located on the transformer's primary side, making the coherer more
> > > sensitive to incoming signals.
>
> That doesn't make sense.  The best any circuit can do is deliver ALL of
> the received power to the load (the "sensitive device", in this case),
> and without a local power supply and active component such as a tube or
> transistor, "regeneration" doesn't make any difference.

I have a little difficulty explaining it myself, but the fact remains that
regenerative receiver circuits are real.  Regeneration is a means of
increasing antenna current by counteracting the resistance of the entire
antenna circuit.  By the introduction of what might be called negative
resistance through the addition of a feedback loop, antenna-field
interaction is increased and energy is absorbed from a greater area of the
incoming wave front.  The basic regenerative circuit is not often used in
present day receiver front ends for a number of reasons, the most
significant of these being an inherent form of instability.  Maximum
sensitivity is achieved at a point just before the detector breaks into
oscillation and this could be initiated by something as simple as wind
shifting the antenna.  As the appearance of oscillating regenerative front
ends on the broadcast bands became a more and more regular occurrence a
decision was made to phase the regenerative detector out of general service.

> Actually coherers and magnetic detectors aren't very sensitive at all.
> The typical coherer requires a signal of the order of FOUR VOLTS to
> operate, with the power depending on the non-conducting impedance.

What do you suppose would happen if you applied, say, 3.999,900 volts across
your cohererer and then transmitted a little RF power from a few wavelengths
away?

> >         Much has been learned about RF propagation since
> >         Tesla's day...

Tesla would probably say, 'not enough.'  In 1919 he wrote:

    "For more than eighteen years I have been reading treatises, reports of
scientific transactions, and articles on Hertz-wave telegraphy, to keep
myself informed, but they have always imprest me like works of fiction. . .
. The Hertz wave theory of wireless transmission may be kept up for a while,
but I do not hesitate to say that in a short time it will be recognized as
one of the most remarkable and inexplicable aberrations of the scientific
mind which has ever been recorded in history."

Gary