which disease?

• To: "'Tesla List'" <tesla-at-pupman-dot-com>
• Subject: which disease?
• From: Tesla List <tesla-at-stic-dot-net>
• Date: Thu, 19 Mar 1998 23:37:56 -0600
• Approved: tesla-at-stic-dot-net

----------
From:  Antonio C. M. de Queiroz [SMTP:acmq-at-compuland-dot-com.br]
Sent:  Wednesday, March 18, 1998 10:27 PM
To:  Tesla List
Subject:  Re: which disease?

Arwin wrote:

> > I wound a coil (diam. 4.33", height 33.66") with .35mm wire (AWG 28??)
> > and a total secundary resistance of approx. 155 ohm. I thought that
> > these 790 meters from 2290 turns would give me resonance at 94,8 kHz.
> > Why not???

And why yes? Computing the inductance and self capacitance for this coil
I obtain 20.8 mH and 11.6 pF, what results in resonance at 178 kHz.
The estimation of the resonant frequency by 1/4 wave resonance based on
the wire length (f=c/(4l)) results in an error factor that tends to ~0.5 as
the aspect ratio of the coil is increased.

> > I now get breakouts (>20") at half of the form, distroying my turns.

You are probably tuning the primary to some higher resonance of the coil 
instead of the 1/4 wave resonance. Try to reduce the resonance frequency of the
primary. Add more turns to the primary (easier) or use a larger primary
capacitor.

Antonio Carlos M. de Queiroz
http://www.coe.ufrj.br/~acmq

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