# Re: 3/4 wavelength secondaries

```Tesla List wrote:
>
> >From sgreiner-at-wwnet-dot-comThu Jul 18 22:44:31 1996
> Date: Thu, 18 Jul 1996 16:29:39 -0700
> From: Skip Greiner <sgreiner-at-wwnet-dot-com>
> To: tesla list <tesla-at-pupman-dot-com>
> Subject: 3/4 wavelength secondaries
>
> Hi everyone
>
> I wonder if anyone has ever tried to wind a secondary at 3/4 wavelength
> rather than 1/4 wavelength.
>
> It appears that it may not be possibe to wind a 1/4 wavelength coil that
> will resonate at the correct frequency without using the large terminal
> capacitance. Perhaps a 3/4 wave coil could be made.
>
> I would appreciate any comments.
>
> Skip

Skip,

Absoluetly!  It'll work... for a little while.  You see, at the 1/4 wave
point, 1/3 the way up the coil, you would get an arc flashing across the
windings. (Resonant rise)  At 2/3 the way up, you could put you hand on
the coil.  (1/2 wave point- zero volts)  Then at the top you would have
the same voltage as at the 1/3 point (another 1/4 wave node).

Actually all coils (any coil) are 1/4 wave, 1/2 wave, 3/4 wave and full
wave!!!!  (for some specific frequency!)

This is why a mistuned or grossly over-coupled coil arcs up and down its
length!  Various other frequencies are also present and find their
natural resonant rise points (1/4 wave points)along the coil and arc
over.

You don't need a toroid to make a coil oscillate at its natural 1/4 point
you only need to dump in a quantity of magnetic or directly coupled
energy at its natural frequency.

No coil will ever oscillate at the quarter wave point predicted by the
wire length equation.  (due to inductance and self capacitance.)

Richard Hull, TCBOR
```