1/4 Wave Theories - What now?

From:  terryf-at-verinet-dot-com [SMTP:terryf-at-verinet-dot-com]
Sent:  Saturday, May 30, 1998 3:09 PM
To:  Tesla List
Subject:  1/4 Wave Theories - What now?

Antonio and All,

Here is my pet theory about resonances capacitances and such. 

        I believe that the self capacitance is the capacitance of the
windings to ground.  Each turn has a capacitance to ground along the length
of the coil.  Each capacitance is separated from the rest by some inductance
depending on where they are located.  This produces all kinds of local RC
networks.  As you tune around the coil you happen upon points were the
resonances add up and cause a peaking effect.  This accounts for the little
resonance points we see during tuning.  The real key here is that all the
currents seem to be in phase along the coil.  No big standing waves as we
have all thought in the past.
        I should also point out that there is a voltage node at the base of
the secondary simply because it is grounded there :-)  This zero voltage
point has nothing to do with any standing waves.  The currents in my tests
clearly show that the top and bottom secondary currents are in phase.  Of
course, the current and voltage are 90 out of phase as in any LC network.
        The current at the top of the coil is about 65% of the current at
the base.  I believe this is due to the current splitting between the top
terminal and the self capacitance.
        This is all rather new so there are still details to be worked out.
I have not seen any big problems with this so far.


        Terry Fritz

At 11:24 PM 5/29/98 -0500, you wrote:
>From:  Antonio Carlos M. de Queiroz [SMTP:acmq-at-compuland-dot-com.br]
>Sent:  Friday, May 29, 1998 8:12 PM
>To:  Tesla List
>Subject:  Re: 1/4 Wave Theories - Trash Them!
>Terry Fritz wrote:
>> These measurements indicate that the secondary is
>> acting as a simple lumped inductor.  There appears to be no 1/4 wave effect.
>> The currents are in phase.  It appears that the 1/4 wave theory of Tesla
>> coil operation is incorrect.  Also, the top terminal appears to be acting as
>> a simple capacitor in parallel with the coil's self capacitance.  A model
>> for this behavior is presented.
>If the top capacitance is significantly greater than the "self-capacitance",
>the behavior is very precisely the one of a lumped circuit. Without any top
>capacitance, 1/4 wave resonance is a better model, but the difference between
>an open-ended (rather peculiar) transmission line and a lumped circuit is
>negligible, at that first resonance. To verify clearly that a resonator is
>a transmission line, try to find other resonances above the main resonance.
>There should be another at a frequency that is between two and three times
the main
>resonance without top load (f0), depending on the top load capacitance, and
>above, separated by somewhat less than 2f0.
>I can easily count more than ten in a test coil.
>(I will be out of the list for the next week)
>Antonio Carlos M. de Queiroz