Re: [TCML] 1/4 wavelength theory ??

["Shaun Epp" <scepp@xxxxxxx>]

Thanks to all that responded to my questions.  

It's funny that some of the computer tesla coil programs still mention the topload capacitance to tune for 1/4 wavelength.  That's was why I ask this question.  

thanks,

Shaun Epp




-----------------------------------------------------------------------------------------------------------------------------------------------------------------
Date: Sun, 07 Feb 2010 06:43:57 +0000
From: Paul Nicholson <tcml88@xxxxxxxxxxx>
Subject: Re: [TCML] 1/4 wavelength theory ??
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Message-ID: <4B6E612D.4000803@xxxxxxxxxxx>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

The electrical length of the wire is shortened when it is
wound into a coil.

Here's a chap who got it right - back in 1994.  From the list
arcs,

  http://www.pupman.com/listarchives/1994/november/msg00041.html

dwp wrote (Nov 94):
 > 1/2 wave of wire, wound as a solenoid, "looks/acts" like a 1/4 wave.
...
 > The exact frequency will depend on the length to width ratio...

 > For tall skinny coils, it tends to 2-1.  For shorter fatter
 > coils it tends back towards to 1-1 but does not get there.

Here's the actual curve which relates the wire's wound velocity
factor to that of the straight wire

  http://abelian.org/tssp/ph1.gif

All this applies to the unloaded coil.  If you add a big toroid the
frequency will be pulled down a lot, maybe to reach near the frequency
expected from the straight-wire.  This might explain some persistence
of the 'quarter-wave of wire' myth.
--
Paul Nicholson
--
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla