Re: 1/4 wave theory

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

Original poster: "Peter Lawrence by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Peter.Lawrence-at-Sun-dot-com>

Michael,
        fear not!, while this particular question has come up before, it has
been shown both experimentally and theoretically that 1/4 wave length wire
is irrelevant to TC performance. The resonant frequency of a TC secondary
is a function of its inductance and its self capacitance, and not on any
magical length of wire.

The 1/4 wave length "theory" comes from the thought that signals travel in
a straight wire at the speed of light (or something related to it, slightly
less for various choices of conductor). BUT, in a TC the wire that would be
100 feet away in a straight line antenna (where 1/4 wave theory does apply)
will only be a fraction of an inch away in a TC coil, and the inductive 
and capacitive coupling between those portions of the coil that are 100 feet
appart wire length wise are "much closer" in the electrical (and physical)
sense. So the propagation speed of signals along a coil do not have anything
to do with the propagation speed in straight wire.

-Peter Lawrence.


>Original poster: "McQuay, Michael by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
<Michael.McQuay-at-wcg-dot-com>
>
>
>>From what I've gleaned from the list so far, I fear I may be about to start
>a holy war, but I'm going to ask anyway.
>
>Is it advantageous to design a coil such that the linear feet of wire in the
>secondary is equal to 1/4 of the operating wavelength?
>
>There, I've pulled the pin.  Let the shrapnel land where it may.
>
>Here's my situation.  I have a secondary that I wound a number of years ago
>that I would like to put into service.  I've never ran this secondary since
>I wound it.  I'd like to build a tank circuit to excite this thing, so I'm
>wondering if I should use the 1/4 wavelength theory to determine the
>operating frequency of my tank circuit or if there's some other method I
>should use for determining my operating frequency.
>
>Specs:
>
>Coil length - 23.625 inches
>Coil diameter - 8.375 inches
>number of turns - 536
>wound with #22 magnet wire
>spaced such that there are about 22.5 turns per inch
>linear feet of wire - 1174.6 ft.
>
>>From everything I'm seeing on this maillist (and associated websites), it
>looks to me like I may not be able to get very good performance out of this
>coil without rewinding it with more turns.  Comments?
>
>Michael McQuay
>
>
>