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>

Paul,

Thanks for helping to straighten me out in regards to the subject, for
example where I wrote:

> > Not if you're trying to reproduce the results which Tesla
> > reported so assertively.
>
> Except that he never reported any results.  The idea is flawed,
> but Tesla couldn't see that. . . .

I should have written something like ". . . the results which Tesla implied
. . ." -- sorry.

> Let me try and describe the situation re power transfer.
>
> Tesla wanted to force current through the ground such that to the
> earth, it would appear as a monopole radiator, ie a point source of
> alternating charge at the earth connection.  This alternating
> point source would cause a conduction current to ebb and flow
> radially from the earth terminal, thereby inducing alternating
> currents in a receiving ground terminal.
>
> However, conservation of charge means that a monopole radiator
> cannot exist in nature (the term 'monopole' used by radio engineers
> to describe a vertical radiator is a misnomer).  Wherever a
> collection of say +ve charge is assembled, it must be drawn from
> somewhere, which leaves an equal and opposite quantity of -ve
> charge behind.  Thus whenever you try to construct a monopole
> radiator, you find you actually have a dipole instead.  In this
> case, the charge forced into the earth is drawn from the topload,
> and when you look at this, you see that the ground current flowing
> out from the 'monopole ground terminal' is matched by an equal
> displacement current returning from the ground surface back to the
> topload.  Thus we have a complete AC circuit which allows energy to
> be coupled to some device tapped into this loop, eg a receiver TC.

Okay, I follow you.

> So far so good.  Real power can be transferred over a distance by
> displacing charge in this way.  But displacing charges takes
> energy - the conduction currents in the ground turn some of it
> into heat, and both the conduction current and the displacement
> current cause EM energy to be radiated.  Tesla was arguing that a
> suitable arrangement of transmitter could be made to stir up the
> necessary charge displacements in the ground without loosing
> significant power to either EM radiation or to ohmic losses. This
> is realistic only for cases in which the transmitter is intended
> to deliver power to nearby receivers.

I believe Tesla knew there would be a surface wave associated with the
conduction current.  And, he did refer to an EM radiation component from the
elevated structure as loss.  Antenna theory as I understand it indicates
that a quarter-wave Marconi-type antenna consisting of a vertical conducting
rod extending about 1800 feet above the earth's surface and excited at a
frequency of 136 kHz would be a fairly efficient radiator.  It also occurs
to me that a much shorter Tesla-type transmitting structure, say, about 50'
overall height, for the same frequency, the bottom third or so consisting of
a helical resonator followed by a relatively large conducting cylinder
connected to a spherical or torriodal terminal of large surface area, would
not be as efficient a radiator.

I'd like to ask a few questions.  You wrote of loss due to the conversion of
a portion of the energy of the conduction currents into heat.  Would this
process take place primarily in the vicinity of the transmitter's ground
connection?  Assuming a near ideal ground connection, how would you
characterize the performance of the system?  Does it make sense to talk
about the impedance of a ground connection or is it better to refer to it's
resistance?

> The difficulty becomes apparent when you look at the efficiency of
> the transfer.  At short ranges (much less than a free-space
> wavelength) the arrangement can be modeled by an equivalent
> circuit, such as
>
>    (TX topload)---------||---------(RX topload)
>            |          |      Cc    |         |
>            |          |               |         |
>         [TX coil]    ===Ct           ===Cr   [RX coil]
>            |          |               |         |
>            /          /               /         /
>            \Rt      \Rtg         \Rrg  \Rr
>            /          /               /         /
>            \          \               \         \
>            |          |     Rc     |         |
>    -----------------\/\/\/\/\--------------------
>    ///////////////////////////////////////////////////////
>
> I've shown various resistances which represent coil losses and
> ground conduction losses.  Ct and Cr represent the bulk topload
> capacitances of each resonator, and Cc is the coupling capacitance.
> Rr is the receiver's loss resistance which includes the useful
> load.
>
> The coupling coefficient is Cc/sqrt(Ct*Cr) and at ranges greater
> than about a topload-height, Cc becomes very small compared with
> Ct, so that the receiver only intercepts a small proportion of the
> transmitter's circulating current.  Even at these short ranges,
> the majority of the input power is dissipated in the transmitter's
> loss resistance Rt and the ground losses represented by Rtg. If
> at the same time you demand a high loaded Q factor in the receiver
> coil, you'll get a similar decimation of efficiency added in there.
>
> The upshot is that the efficiency is lousy, even at very short
> range.  This is so, even if the transmitter is small compared
> with the wavelength so that there is negligible far field
> radiation.
>
> At longer ranges - a wavelength of more, we can no longer describe
> the system by a simple equivalent circuit and it becomes better to
> think in terms of the capture area of the receiver coil.  This
> area, which might be a few hundred sq metres for a large receiver
> will only intercept an amount of power proportional to its capture
> area divided by (4*pi*range^2). Thus the coupling coefficient is
> very small indeed for any decent range.

It it reasonable to assume the capture area could be increased by some
technique that would increase RF current flow in the receiver coil, such as
regeneration?

> So realistically, you must forget power transfer, signals yes, but
> useful power no.

That's good to hear, although I still not convinced the telecommunications
application is real.  I expect a lot will depend on the quality of the
ground connection.

> However, there are ways around this.  The transmitter could
> focus its radiation in the direction of the receiver, eg using
> dish antennas, but these are impractical except at high frequency.
> For low frequencies, some sort of waveguide can increase the
> coupling dramatically.  One way to do this is to string a
> conductor between transmitter and receiver.  Currents induced in
> this wire guide the waves efficiently to the receiver.  As it
> happens if you look at the currents and voltages induced in this
> wire, they happen to be exactly what you'd expect from an
> overhead transmission line - it makes no difference if you think
> of a line carring power by virtue of its voltages and currents, or
> if you regard it as a guide for energy carried in the EM field.
> So it's fine to think of the connecting conductor as a guide to
> the radiated energy which concentrates it at the receiver. In a
> sense, we are already using Tesla's power distribution scheme,
> continent-wide, but with the enhancement of guided waves[*].
> Without this or some other mechanism, the coupling at any useful
> range is minute and the efficiency almost zero.

Tesla would be the first to acknowledge the presence of a conductor between
the elevated capacitances would be critical to the success of his industrial
power transmission scheme.  All of the related writings refer to it.  The
ground-only method is given just minor attention in the patents.

> Another way to get around the small coupling coefficient is to
> enclose the entire system of transmitter and receiver, and the
> space in between, inside a lossless cavity.  Then the cavity can
> fill with radiation to a point where the tx and rx are in
> equilibrium as far as their exchange of energy is concerned.
> Efficient power transfer under these conditions is only possible
> with a high-Q cavity, but the sometimes proposed cavity between
> earth and ionosphere is far too lossy to qualify, at any frequency.
>
> And as for EM radiation - if you want a transmitting TC to spread
> it's displacement current field over a range anything approaching
> a wavelength or above, then you cannot avoid significant EM
> radiation...
>
> Gary wrote:
> > http://www.tfcbooks-dot-com/writings/w_system.htm.
>
> ...unless that is you believe in some of the pseudoscience in the
> cranky books for sale here?  21st century snake oil! Caveat emptor.

Once again, please accept my sincere apology.  I'm really trying to get this
right.  If you would let me know the offenders I will immediately modify the
annotations to reflect such concerns.

> And I wrote:
> > And what is meant by a 'slow-wave' resonator?  Does the adjective
> > mean anything?
>
> Jim wrote:
> > Some structure along which a wave propagates at less than free
> > space.
>
> For EM waves, that applies to all physical structures.  Can you
> make a fast-wave helical resonator?  Hence my feeling that the
> term is redundant, although it sounds impressive.
>
> Jim wrote:
> > Corums used the terminology when describing their (now
> > deprecated) theories of TC function (basically a 1/4 wave
> > transmission line much shorter than free space 1/4 wave because
> > propagation is in a "slow wave structure")..
>
> I disagree, that's about the only bit they got right in their
> 'Class Notes' paper.  The rest is worthless or wrong.

Have you considered working up a critical response to the paper?  I'm
certain that everyone concerned would benefit from the peer review.

> > Terry's measurements of voltage and current phase at top and
> > bottom of secondary, and your modeling work, have pretty much
> > shot that theory down.
>
> Terry's phase measurements in fact are quite consistent with the
> representation of a solenoid as a transmission line, or as a lumped
> element - take your pick. They neither confirm nor refute that
> part of Corum's theories. The unequivocal confirmation comes from
> the existence of a mode spectrum rather than just a single
> resonance.
>
> [*] And Tesla wrote:
> > you will use a very low frequency so that the loss in these
> > electromagnetic waves . . . should be minimized. . . .
>
> which at 50-60Hz we do indeed!
> --
> Paul Nicholson

Gary Peterson