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

[Paul Nicholson <tcml88@xxxxxxxxxxx>]

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
--

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