Re: SSTC As a transmitter.

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

Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>" <davep-at-quik-dot-com>


>>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?


	Both have there places.  Resistance is lossy, to the
	extent that power is lost, working with resistance has
	its advantage, i should think.

 
>>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?

	What is meant by 'regeneration'?
	If the reference is to the common regenerative receiver,
	this uses a LOCAL POWER SUPPLY.  All the 'output'
	energy in a regenerative receiver comes from the
	local PSU...


>>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.
	Its real.  It works.  Its radio.

	(Tesla might have disagreed....  Its 100 years later...
	much has been learned.)


>>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.
	tend to concur..


>>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.

	CONCUR!


>>>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!

	best
	dwp

...the net of a million lies...
	Vernor Vinge
There are Many Web Sites which Say Many Things.
	-me