1/4 Wave Theories - Trash Them!

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 others
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