RE: 1/4 wave theory/cite the variance?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "David Thomson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dave-at-volantis-dot-org>

Paul, Terry, et al,

Perhaps your modern view and Tesla's view are both right?  The arguments
being brought up in favor of an adjustment to quarter wave are based on
tightly wound coils with self-capacitance and tightly coupled inductance
between the wires.

If you'll look carefully at all the pictures in CSN, you will see that all
of Tesla's coils are space wound, thus eliminating the effects you're
mentioning.  Also, Tesla utilizes space winding on his large flat spiral
secondary.  This should be a significant consideration when discussing
quarter wave in relation to Tesla's work.

Dave

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Saturday, February 16, 2002 1:33 PM
To: tesla-at-pupman-dot-com
Subject: Re: 1/4 wave theory/cite the variance?


Original poster: "Paul Nicholson by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<paul-at-abelian.demon.co.uk>

Hi Harvey,

> pray tell me what this deviance from
> quarterwavelength actually consists of? Is it 10%
> lower? Is it 15% by added top polar capacity? Is it no
> known figure of percentage basis compared to that
> quarterwavelength value,

The 1/4 wave resonant frequency of a wire, when wound into a
solenoid, is typically more than 50% higher than that of the
straight line value.

The extraordinary persistance of the wire-length myth comes
from the willingness of people to accept things on faith without
making even the most basic of cross checks.

Take a typical TC secondary and measure its unloaded Fres.
Compute the free space 1/4 wave length and compare it to the
wire length.

For example, Terrys 30" coil, in metric units:

 Diameter: 0.261 metres
    Turns: 1000

therefore wire length = 0.261 * PI * 1000 = 820 metres.  Now this
is a quarter-wave in free space at 300x10^6/(820 * 4) = 91.5 kHz.

When you measure this coil, the actual Fres is 148 kHz.  If you'd
tuned your primary to match an expected 91.5khz, it simply wouldn't
work.  This sort of difference is typical, and the difference gets
greater as the H:D ratio is reduced.

There, that was a simple check that could have been done by anyone
in the last 10 decades.  You can't afford to rely on faith in this
business.  Criticism, checks, cross-checks, and more checks.
Absolutely essential.  Makes it darn hard to make reliable progress
if you're working alone.  Thank goodness for this list.  This is the
first time in the history of Tesla coiling, as far as I know, that
so many people (800+ now I believe) have come together in a rational
forum to compare notes and ideas.  We are very privileged to live in
this era of Pentiums and pupmans.  Lets try to do justice to that
position.

See the comments and graph in
 http://www.abelian.demon.co.uk/tssp/misc.html

> I submit that this is mere jumping on a bandwagon of derision

No, science doesn't work like that. The bottom line is: Nature Rules.
--
Paul Nicholson
--