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Dump the Lump
Hi all,
This is just a follow on from my previous posting.
Reading it again I have probably clouded the explanation with a host of side
issues. So I will start again.
1) As in most transmission line all signals travel along the Tesla coil with
the same definite velocity. This is true of all signals with frequencies
from DC up to perhaps 100MHz. So this includes the resonance frequency of
the coil and all its harmonics. In the case of a Tesla coil the velocity can
be a thousand time slower than the velocity in a an open wire. This has been
verified mathematically, modellingly and by experiment. There is no
evidence to suggest that this is not true or to suggest that any signal can
instantly travel down the coil. . Probably the most convincing evidence is
obtained by performing an experiment with a signal generator, scope and
coil.
You will be able to verify directly that no instant transmission occurs up
to the limit of your generator and scope assuming that is no more than say a
100MHz. If you require advice on how to set up such an experiment I am
willing to help.
I challenge anybody who believes different and wants to argue the point with
me, to do the experiment, as I have done, and show that instant or fast
transmission occurs. It should be possible to perform the experiment in less
than an hour.
2) Given that all signals (up to a limit) including those with a frequency
of that of the fundamental resonance of a Tesla coil travel along the coil
with a slow velocity, the simplest explanation of the fundamental resonance
and higher order resonances is that they are standing wave resonances
caused by reflection from the end. This also explains how a coil that is
shorted at both ends can resonate.
Note. The velocity is not strictly constant it can vary with frequency
caused by frequency dependent losses and dielectric constants. This is
called dispersion. In addition at high frequencies when the individual
turns become resonate new effects occur. For the average Tesla air cored
secondary coil wound with copper wire I would not expect the dispersion to
produce any more than a few percent change in velocity up to say 10Mhz and
the high frequency resonances will not occur until the wavelength (in air)
approaches the length of one turn.
The above assumes that the secondary is wound as a single helical coil.
Do the experiment Terry, I know you love them. and put the results on your
site. You will have the first definitive paper proving it one way or the
other. Although I suspect it may just produce an interpretation debate.
We can then take the parameters of the coil you have used and convert them
to a transmission line model and get some one to plug them into microsim or
spice. For my part I can use them in a theoretical calculation.
We will then have our own proof mathematically, modellingly and by
experiment. If anybody in the Orlando (Fl US) area needs help to do the
experiment I am willing.
Down with the lumped theory, long live the transmission line theory. Am I
biased, yes, but then I've done the experiment and more. Come on guys get
with the programme Dump the Lump.
Just in case somebody still misunderstands me this has nothing to do with
how you model a Tesla coil it's how one resonates. Looking into the driving
end of a transmission line near resonance it has an impedance identical to a
tuned circuit and hence it is perfectly reasonable and convenient to use
such a representation in a model. But it is only a representation.
Bob