Re: A photographic tutorial of Pancake Coil winding...with movies...(fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Fri, 22 Jun 2007 07:56:44 -0600
From: Gary Peterson <g.peterson@xxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: A photographic tutorial of Pancake Coil winding...with
    movies...(fwd)

Paragraph #19 of "High Frequency Oscillators for Electro-therapeutic and 
Other Purposes," Electrical Engineer, November 17, 1898 located at 
http://www.tfcbooks.com/tesla/1898-11-17.htm relates to this discussion.

http://www.tfcbooks.com/images/articles/1898-11-17/figs_5678.gif

"One or two observations made while pursuing experiments with the apparatus 
described might be found as deserving mention here.  As before stated, when 
the oscillations in the primary and secondary circuits are in synchronism, 
the points of highest potential are on some portion of the terminal T.  The 
synchronism being perfect and the length of the secondary coil just equal to 
one-quarter of the wave length, these points will be exactly on the free end 
of terminal T, that is, the one situated farthest from the end of the wire 
attached to the terminal.  If this be so and if now the period of the 
oscillations in the primary be shortened, the points of highest potential 
will recede towards the secondary coil, since the wave-length is reduced and 
since the attachment of one end of the secondary coil to the ground 
determines the position of the nodal points, that is, the points of least 
potential.  Thus, by varying the period of vibration of the primary circuit 
in any manner, the points of highest potential may be shifted accordingly 
along the terminal T, which has been shown, designedly, long to illustrate 
this feature.  The same phenomenon is, of course, produced if the body of a 
patient constitutes the terminal, and an assistant may by the motion of a 
handle cause the points of highest potential to shift along the body with 
any speed he may desire.  When the action of the coil is vigorous, the 
region of highest potential is easily and unpleasantly located by the 
discomfort or pain experienced, and it is most curious to feel how the pain 
wanders up and down, or eventually across the body, from hand to hand, if 
the connection to the coil is accordingly made--in obedience to the movement 
of the handle controlling the oscillations.  Though I have not observed any 
specific action in experiments of this kind, I have always felt that this 
effect might be capable of valuable use in electro-therapy."


----- Original Message ----- 
> From: David Thomson <dwt@xxxxxxxxxxxx>
>
> Hi Bart,
>
>> >Bart just pointed out that the metal pipe you are using acts like a
>> >waveguide, or third coil.
>
>> Just the opposite. A third coil not in resonance acts more
>> like a capacitively coupled topload object and the dimensions
>> of the coil. The third coil is pretty much a pipe at that
>> point. In Jeff's case, it's nothing more than a topload
>> object. In your coil, the solenoid is acting like Jeff's pipe
>> (just a topload object).
>
> It may be an opposite perspective, but it is the same thing, either way.
>
> A third coil has no inductive coupling with the secondary and acts like a
> Helmholtz resonator.
>
> If my understanding is correct, anybody can replace the third coil on 
> their
> magnifier with a copper tube of the same dimensions and get the same
> results.
>
> Dave