Re: Tesla Coil RF Transmitter

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Dan" <DUllfig@xxxxxxxxxxxxx>

Jim:

Ok, I should not have brought up the whole LC tank thing, as it was 
an unnecessary detour from my main point. I only brought it up 
because you said that an LC tank circuit was an example of a resonant 
system without standing waves, and I think there is indeed a standing 
wave in an LC tank at resonance!

But in regards to the Q of the earth, so far all we do is measure the 
amplitude of the Schumann frequencies passively, instead of pumping 
8Hz of power into the ground and see what happens. How do we know how 
much energy is driving the earth? What is the main mechanism that 
drives it? if it is lightning, are separate strikes canceling each 
other out? Whithout knowing exactly how much energy is being put into 
it, how are we going to know the attenuation?

We know of one person that tried to directly drive the earth at its 
resonant frequency, and that was Tesla. He said that based on his 
experiments, he thought he could transmit power all over the globe. 
Did he have the data to back up his assertion? I don't know, but I 
think at the very least we should be trying to duplicate his work, 
which I think to this day has not been done.

Dan
----- Original Message -----
From: <mailto:tesla@xxxxxxxxxx>Tesla list
To: <mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx
Sent: Sunday, September 25, 2005 5:12 PM
Subject: Re: Tesla Coil RF Transmitter

Original poster: Jim Lux <<mailto:jimlux@xxxxxxxxxxxxx>jimlux@xxxxxxxxxxxxx>

At 01:17 PM 9/25/2005, Tesla list wrote:
>Original poster: "Dan" <<mailto:DUllfig@xxxxxxxxxxxxx>DUllfig@xxxxxxxxxxxxx>
>
>Jim:
>
>Two issues to bring up. First, earth as a resonator:
>
>Standing waves are THE definition of resonance in a sphere. There is
>no known mechanism by which a sphere can show increased response to
>certain frequencies, and not have standing waves.

I can think of at least one. Cover the sphere with a material that is
frequency selective (in terms of its absorption vs frequency). Such a
material exists: the ionosphere.


>  When you look at a Schumann resonance spectral chart, you see
> peeks in frequency response that correspond very nicely with what
> would be expected if you divide the speed of light by the
> circumference of the earth. But you are saying that these peaks are
> due to some not-yet-explained phenomena.

Not at all.. All I a am saying is that the peaks do not imply a
resonance. A implies B, but B does not imply A.  (Not B would imply Not A)


>  Your implication fails Occam's razor too! ( they don't call it
> "Schumann Resonance" for nothing :)
>
>The only reason you don't want to accept that the earth resonates,
>is that you are not comfortable with the implication: global power
>distribution.

hardly.. I see so many practical problems with global power
distribution on so many levels that I'm not willing to give it a
whole lot of thought (rodent fuzzy behind comes to mind).

HOWEVER, I am willing to entertain analysis and/or measurement that
shows it's possible, within the confines of physics as currently
understood (i.e. no resorting to "special things")


>  You say the attenuation is too great, that the earth has a low Q.
> But if waves don't make it all the way around the earth, there are
> no standing waves.

Waves CAN make it all the way around the earth. I've personally made
and observed them (as have many others) However, the loss in the path
was phenomenal.

Consider a classic microwave circuit used for high power breakdown
testing: the resonant ring.  You build a loop of waveguide that is an
integral number of wavelengths long (typically, there's a trombone
section in there somewhere, so you can "dial it in").  You start
injecting power and the circulating power increases until the power
lost in one transit equals the power inserted.  Say, for instance,
that the loss is 10% (about 0.5 dB).  If I put one watt into the
system, eventually, the circulating power will be 10 watts.  This
system has a Q of 10.

If the system is a bit lossier.. say it loses 50% of the power.  Then
I'll only get 2 watts circulating  when I've put in 1 watt.  Thats a Q of 2.

Now, however, look at long path HF (for an example). You might
transmit 1000 W (+60dBm), and receive -150dBm, for a path loss of a
mere 210 dB. (Hey, it's a lower path loss than a earth/moon/earth
reflection)  The loss is 99.999 99999 99999 99999 9% (I might be off
by a 9).  By any normal measure, this would not be considered a
resonant system.  It would be considered a "dummy load" and a very
good one at that.

However, if I were to sweep my transmitter over frequency, even with
that phenomenal loss, I'd notice that there was a definite frequency
dependent effect, and a fairly narrow band one, at that.  I don't
have the data in front of me, but I'd hazard a guess that the
bandwidth of the peak is less than a MHz (with a peak frequency of
10-20 MHz).  By the usual Center Frequency/Bandwidth measurement of
Q, this would imply a Q of 10.  But it's not.


>And without standing waves, there is no resonance. Without
>resonance, the earth would have equal frequency response to all
>frequencies, BUT IT DOESN'T!

Again.. frequency selective absorption exists in all kinds of
materials, with no resonance (at least at frequencies near the
frequencies being absorbed) needed.  Selectivity does NOT imply
resonance.  Conversely, it doesn't imply that there isn't resonance.

>Second, LC tank circuits as lumped circuits:
>
>There is a tendency to think that just because a formula accurately
>predicts the outcome of an event, that the formula "explains" what
>is going on. This is not so.

True. However, if the formula is based on the underlying physics,
there's a reasonable presumption that it explains the phenomenon.


>Just because lumped circuit calculations can predict the resonant
>frequency of an LC tank circuit, does not mean that an LC tank is a
>lumped circuit.

The LC formulas work for infinitely small lumped components (where
the size is a tiny fraction of the wavelength).

>  At resonance, the electrical charge is bouncing back and forth
> between the two sides of the capacitor, passing through the
> inductor on its way back and forth. By definition, the voltage HAS
> to be higher at the capacitor plates than it is at the center turn
> of the inductor coil. You admitted as much without even realizing:
> you said that there was uneven current distribution. Lumped circuit
> calculations assume up front even current distribution!

There's an uneven distribution in the typical tesla coil, because of
distributed capacitance.  There isn't an uneven distribution in the
run of the mill lumped LC.  If I build an audio frequency LC resonant
circuit using a iron core inductor and a small ceramic capacitor, the
fields are uniform, at least to the measurable limit.


>These kind of approximations are done in physics all the time,
>because the difference between an approximation, and an accurate
>description, is so small that the extra effort is a waste of time.
>The formula for the period of a pendulum only holds true for small
>arcs of swing.

Funny thing, that,... In high school I spent some amount of time
deriving an exact formula for the pendulum (i.e. not using the small
angle approximation) in order to determine the change in period due
to the gravitational pull of the moon and/or sun.

However, the LC model for a lumped circuit is not an approximation of
a transmission line system.  One can account for all the parasitics,
also as lumped components, and get an exact solution.

>  When we push a car, we figure out acceleration by assuming it is
> going in a straight line, but in fact it is moving in a 17500 km
> circle! An LC tank circuit at resonance is not really a lumped circuit,

it isn't?  How far different is it?  What model would you propose
instead?  Sure, one can model it using FDTD methods and break it up
into tiny cells using Yee's model (which is transmission line based),
but it's hardly a single transmission line.  And, I venture to say
that a FDTD model isn't any better, nor does it provide any
additional intuitive insight, over the lumped model.

>but the lumped circuit calculations give numbers that are so close,
>why bother with more accurate formulas? But never forget that lumped
>circuit calculations are approximations that give reasonable
>numbers, not a description of what is going on.


Look.. Tesla's writings imply that this resonance phenomenon is not a
parts per billion kind of effect, or else it wouldn't be practical
for worldwide power distribution.  Tesla certainly implied (if not
explicitly said) that his scheme was practical, and he had a very,
very good knowledge of what "practical" means.

Your claims of the non-fidelity of lumped models for LC are at the
ppm or ppb level. If you start bringing in all sorts of deviations at
any level, then should we not start worrying about including
relativistic effects? What about controlling for thermal effects (the
temperature coefficient of resistance is in the 1 part in 1E5 range
for most metals).  What about magnetostriction?  The magnetic and
electrostatic fields in TC will cause dimensional variations
substantially larger than that.  Folks who design busbars in power
substations worry about such things.

If Tesla's ideas have any possibility of being practical, then they
should be readily detectable, and should be predictable using simple analysis.



>Dan
>
>----- Original Message -----