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Re: magnetic core
In a message dated 97-02-01 02:59:11 EST, you write:
<< >To: tesla-at-pupman-dot-com
>From: Joe Cummings <joecmn-at-globalnet.co.uk>
>Subject: magnetic core
>
>Some years ago I built a tesla coil from a motor car spark coil and what
scraps I could muster. I was disappointed at the results, but didn't have a
great deal of money at the time. However, when you're skint(broke) you
think!
>
>I reasoned that if the coil was operating at radio freqency, then a ferrite
rod such as is found in portable radios might enhance the effect. The only
ones that were available were about 10-15cms. in length and about 7.5mm in
diameter. When I inserted the ferrite rod into the core I was gratified to
see an intensification of the effect.
>
>Has anyone tried this? I thought it might be possible to use ferrite
powder in a glass tube for a bigger coil, but I now believe that the
magnetic properties are imparted to the ceramic in the heating process.
>
>For a discussion of ferrites and further references, see Kirk-Othmer,
Encyclopedia of Chemical Technology, publishers Wiley Interscience.
>
>Best wishes,
>
>Joe Cummings
>
>>
Joe,
I have used ferrite to increase secondary inductance, to increase the
coupling coefficient, and as a tuning aid, in tube coils. I didn't really
see much improvement in coil output. Some have suggested that losses in the
ferrite can be quite high (maybe higher in a tube coil due to higher
operating Q?)--I welcome all viewpoints on this.
Lou Balint of PA uses ferrite in his magnifier drivers, and he is continuing
to explore its possible benefits. It is important to have the "right" kind
of ferrite for the frequency and permeability requirements. By using
ferrite, we may be able to build more compact coils, I would think.
Thanks for the reference and info.
John Freau