# Re: Resonant frequency of twin coil? (fwd)

```---------- Forwarded message ----------
Date: Mon, 16 Jul 2007 19:00:09 -0300
From: Antonio Carlos M. de Queiroz <acmdq@xxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Resonant frequency of twin coil? (fwd)

Tesla list wrote:
> ---------- Forwarded message ----------
> Date: Mon, 16 Jul 2007 08:20:07 +0000
> From: Nicolas Alstrup <n_alstrup@xxxxxxxxxxx>
> To: tesla@xxxxxxxxxx
> Subject: Resonant frequency of twin coil?
>
> Hi,
>
> I havent been able to find any information on this on the web.... I am in
> doubt how to calculate the resonant frequency for a twin coil, or rather how
> to tune it - any help appriciated....
>
> This is my schematic:
>                                                   __                    __
>                                                  /    \                 /
> \
>                                                  \__/                  \__/
>                                                    |                       |
> -------------------------------------| |-----------|-------------------   |
> |                  |               cap       |   |                  |   |
> |                  |                          c   c                  c   c
> o                 o                          c   c                  c   c
> HV in              spark gap            c   c                  c   c
> o                 o                          c   c                  c   c
> |                  |                          c   c                  c   c
> |                  |                           |   |                  |   |
> ----------------------------------------------------|-------------------   |
>                                                     |_____________|
>
> And these are my specs:
> Secondary coil:
> Each SC consist of apprx. 780 turns of 0,315mm wire. Diameter 60mm, height
> 270mm
> Calculated selfcapacitance= 4,282pF
> Calculated resonant frequency for each coil: 444,257 kHz
>
> Primary circuit
> HV input, NST: 8000V ,  50mA
> MMC capacitance: C=0,0204uF
> Flat Helical coil: inner diameter: 70mm, Wire diameter: 2mm, wire spacing:
> 1mm
>
> My question now is: How many turns on each primary coil? Should I just
> calculate the resonant frequency as if there were just one secondary and aim
> at 444,257 kHZ (that is around 7 turns) or how to do it?
>
>
>
Make the calculations as if your primary capacitor had one half of its
capacitance.

Antonio Carlos M. de Queiroz

```