# Re: Fw: 1/4 wavelength

```Tesla List wrote:
>
> Original Poster: "markjons" <markjons-at-bright-dot-net>
>
>
> -----Original Message-----
> From: markjons <<mailto:markjons-at-bright-dot-net>markjons-at-bright-dot-net>
> To: <mailto:tesla-at-pupman-dot-com>tesla-at-pupman-dot-com
> <<mailto:tesla-at-pupman-dot-com>tesla-at-pupman-dot-com>
> Date: Wednesday, December 30, 1998 2:42 PM
> Subject: 1/4 wavelength
>
> I have a question about secondary windings. According to a chart I found
> from Chris Hill, a 4" diameter secondary has 774
> feet of wire to make the coil.  However the given resonant frequency is 540
> khz.  According to a different web page I found,
> the length of wire in a secondary should equal the 1/4 wavelength, which
> for 540 khz is 454 feet.  what gives? Am I missing
> something here?  any info much appreciated.  markjons-at-bright-dot-net

The latter formula has no relevance to a helical wound coil - ignore it.
The resonant frequency of a secondary coil will be a function of its
self-capacitance and inductance, and its actual resonant frequency will
always be higher than that of a stretched out straight wire (to which
the latter formula applies).

-- Bert --

```