# Re: Lprimary tuning calculation

```Original poster: "K. C. Herrick" <kchdlh@xxxxxxx>

```
That sounds like a good idea! Perhaps one might do that--at least, with a s.s.t.c.--while operating the coil at very low power. Then the primary could be optimally tuned while--necessarily--being physically close to it, without risking a "zap".
```
KCH

Tesla list wrote:
```
Original poster: "S&JY" <mailto:youngsters@xxxxxxxxxxxxxxx><youngsters@xxxxxxxxxxxxxxx>
```
The empirical equivalent is to attach a length of wire, e.g. 4 feet long, to
the secondary toroid, and suspend it outward with a piece of string to act
as if it was a streamer.  The wire length should be the same length as the
streamer length you expect.  This adds a few pF of  psuedostreamer
capacitance, the same as a real streamer would do.   Then measure the
secondary frequency and match the primary to it.  This should result in very
good tuning, and can be done without the need to power up the coil.

--Steve Y.

----- Original Message -----
From: "Tesla list" <mailto:tesla@xxxxxxxxxx><tesla@xxxxxxxxxx>
To: <mailto:tesla@xxxxxxxxxx><tesla@xxxxxxxxxx>
Sent: Sunday, May 28, 2006 11:46 AM
Subject: Lprimary tuning calculation

```
> Original poster: Terry Fritz <mailto:laptop@xxxxxxxxxxxxxxxxxxxxxxx><laptop@xxxxxxxxxxxxxxxxxxxxxxx>
```>
> Hi All,
>
> We know that the primary system needs to be tuned about 5% lower than
> the secondary due to streamer loading.  While playing with ScanTesla,
> I realized that the streamer loading and how it affects tuning is
> fairly straight forward.  A very good estimate (1%) of tuned Lprimary
> inductance is:
>
> Lp = Ls x (Cs + Ca) / Cp
>
> Where:
> Lp = Primary coil inductance
> Ls = Secondary coil inductance
> Cs = Secondary capacitance
> Ca = Arc capacitance = 1pF / foot of streamer
> Cp = Primary capacitance
>
> Almost all of the secondary frequency drop is due to the capacitance
> of the streamer and the 220k part of the streamer load is fairly
> insignificant.  Thus we can simply add 1pF/foot of capacitance to
> Csecondary for the calculation.
>
> Cheers,
>
> Terry
>
>
>
>
>
>
>

```
```

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