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Re: Best sparks (fwd)
---------- Forwarded message ----------
Date: Tue, 7 Jul 1998 17:40:41 -0600
From: terryf-at-verinet-dot-com
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Best sparks (fwd)
Hi All,
>From: "D.C. Cox" <DR.RESONANCE-at-next-wave-dot-net>
>To: Tesla List <tesla-at-pupman-dot-com>
>Subject: Re: Best sparks
>
>to: Terry, Richard, Tesla List
>
>Terry listed an equation regarding the spectral emission from the arc
>itself. This equation listed the RC time constant as a source for the
>generated frequency. This is incorrect. RC time constant is a dissipative
>factor. It will not store energy like an LC time constant value and does
>not support resonance, in fact, tends to reduce or oppose any resonant
>buildup. These three frequencies all listed by Terry are in fact generated
>after the arc discharge travels off the high voltage terminal. In is not
>associated with the capacitance of the sec coil or its inductance.
>Standing waves and transmission line effects are produced in the spark
>discharge itself and the generated frequencies are not associated with the
>fundamental frequencies of the secondary inductor. These frequencies are
>dependent on the geometry and LC constants of the arc channel
Admittedly, I played a little fast and loose with the equation.
Actually, r should have been a complex equivalent impedance. I simplified
it way too much. It is an inductive and resistive component rather than a
simple r. It's magnitude is ~1200 ohms reactive, not resistive. Depending
on the true real resistance value, the equation may or may not make sense
and the dynamic nature of the signal can also make it much more complex than
the simple equation would imply. I have more arm-waving equations (some of
which give exact numbers but I can't support them mathematically). I will
spare you from them for now.
The LC values that would account for these frequencies are rather
low to be associated with purely space charge or atmospheric impedance
effects. In the lightning case, I suspect the capacitance of the cloud, the
resistive dissipation of the lightning strike, and the inductance of the
earth have more to do with the low frequencies than standing waves between
the cloud and ground. However, our exact definitions of "standing waves" may
be conflicting here.
>As Rich Hull points out, lightning is an example of a rich source of RF
>frequencies, however, these frequencies tend to be much lower than
>originally suspected. The Russian scientist, Kapitza, had a theory that a
>considerable amount of UHF power was being generated to produce plasma
>fireballs, and hence, ball lightning. Martin Uman, in his book Lightning,
>discredits this theory with the references listed in his chapter on the RF
>spectrum produced by lightning discharges. The frequencies are centered in
>the low VHF and HF areas with very little power in the UHF bands.
>
>Standing waves are produced between the discharge terminal and the ground
>terminal (or point). As Terry points out in his excellent disertation, a
>Tesla secondary inductor equipped with a large top load torus, ie, large
>terminal capacitance in relationship to the distributed capacitance of the
>coil itself, does not operate with standing waves. It tends to operate at
>one frequency and has no transmission line effects.
In free space, The 1/4-wave wavelengths of the frequencies I see
are: (I should probably use the 1/2-wave frequencies here for this type of
system. But then the distances would be far from believable???)
L = speed of light in feet/second / ( 4 * frequency)
35 feet at 7 MHz
14.5 feet at 17 MHz
7.5 feet at 33 MHz
I have a hard time believing standing waves of these wavelengths are
being set up in my basement (I suspect the losses are too great to support
standing waves). Although 7.5 feet is roughly the ceiling height and 14.5
feet is very roughly the room length, the walls are far from capable of
reflecting RF energy to any great degree (concrete and wood). Also, the
placement of the coil would be awkward for such an effect. If you look hard
enough you may find distances that match but you can also find many that do
not. There is nothing I can see that would account for the powerful 7MHz
signal. However, perhaps the standing wave theory is somewhat supported
here. More testing will tell.
One problem I have with standing waves, is that they need a
prolonged source of reasonably pure single frequency energy in a relatively
low loss well defined system to be created. I don't think a spark channel
is the "nice" kind of place they would be found.
A resonant ring down from a high-energy impulse would be something I
would believe if I could track down reasonable mechanisms to account for the
observations. This is not the same effect as pure standing waves but could
be easily mistaken for standing waves. Perhaps it would be the impulse
input case of standing waves? The abrupt end to the event would be hard to
explain by this mechanism as well as the energy budgets of the signals.
Also remember that there are three frequencies and not just one (at least in
my case). This would also imply that the actual discharge is extremely fast.
In that case, the performance and ability of the top terminal to discharge
in a very brief (nano if not pico second) time would still have great
importance. Also, the over voltage fields I see would be somewhat
explainable by such phenomena. Perhaps it is time to set up the old wave
table from physics 101.....
>The harmonic frequencies as noted by Terry in his coil at 7, 17, and 33 MHZ
>can be surpressed by space winding the secondary inductor, or, as Rich Hull
>has done --- going to extremely large capacitance top loads to force the
>resonator to operate at a single fundamental frequency without a lot of HF
>harmonics.
The secondary is somewhat space wound at 0.030 inches per turn with
0.020 wire. I do not believe the secondary inductor is a factor but I do
believe the secondary terminal characteristics are.
>One final note -- the potential distribution along a sec coil operating
>with a large cap top load is nearly linear in nature and does not simulate
>a sine wave. We have measured this effect with some experiments in early
>1970 when we also started using large capacitance top loads to reduce these
>undesireable harmonics and boost potential output on our larger systems.
>
>I trust this information is of assistance to this thread.
>
>DR.RESONANCE-at-next-wave-dot-net
>
>
>----------
SNIP>>>>>>>>>>>>>>>>>
There is also a chance that the 1200 to 2000 ohm (it varies somewhat
over the discharge) impedance is due to the inductance of the ground loop.
Assuming a 1200 ohm impedance (inductive) at the above frequencies we would get:
Xl= 2 * pi * Frequency * Inductance
At 1200 ohms L=:
7 MHz 27.3 uH
17 MHz 11.2uH
33MHz 5.8 uH
Not unreasonable ground loop values. However is much more likely that the
loop inductance is a single value and the capacitances are what have three
different values. If the top capacitance is 26.78 pF the discharge terminal
is 4.7pF and something else is 1.2 pF all acting into a single inductance
and ringing then the following may be true. Perhaps the above three
capacitances acting into a 19uH inductance is the key?
If the inductance is 19 uH and the capacitances are 26.78, 4.7, and 1.2 pF
we get:
1 / ( 2 * pi * SQRT ( L * C )) = F
1.2 pF gives 33MHz unknown capacitance????
4.7 pF gives 16.8 MHz Ground Ball
26.78 pF gives 7MHz Top terminal
I would think this is the mechanism at work. Of course, this is all
on the very bleeding edge of knowledge so there may be many iterations of
theory before the real mechanism is found. But that is why we are all
here........
I don't know if the transistion times of the ions from the ground
state to higher energy states could have anything to do will all this....
Not my area.... Perhaps someone out there would know??
Thanks for the info on standing waves and such. It is definitly time to put
the calculators and paper down and take some readings of reality.
Are we going nuts yet? I may be starting to feel something!! :-))))
Terry