Re: Questions.

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Gregory Hunter by way of Terry Fritz <twftesla-at-uswest-dot-net>" <ghunter31014-at-yahoo-dot-com>

Hi Josh,

Your post seems to have created quite a bit of
interest, so I guess I'll throw in my $0.02 worth.

--- Tesla list <tesla-at-pupman-dot-com> wrote:
> Original poster: "Joshua H Ball by way of Terry
> Fritz <twftesla-at-uswest-dot-net>" <jhmball-at-juno-dot-com>
> 
> Hello list.
> I've been on the list for a while and am looking to
> build a my first coil
>  in the near future. I have a few questions:
> 
> 1.  What should be a good target frequency for a
> coil?  What are the
> pro's and con's of a higher or lower frequency? 
> What effect does the
> input ac's frequency have?

I'm not sure why you would target a particular
frequency.  Scale the Tesla coil components to your
power supply size and desired spark length, and let
the frequency be whatever it is.  I've built Tesla
coils that operated from 700kHz to 180kHz, and they
all worked great.  The AC input frequency has no
appreciable effect on operating frequency.  A 200kHz
Tesla coil will oscillate at 200kHz no matter what
sort of current it is fed with.

> 
> 2.  I have found some caps I can get for a
> relatively good price and
> would like to use them for my coil.  Are these in
> the right ballpark for
> tesla coils?
> 	  .001 UF 10 KV AXIAL CERAMIC DISC CAPACITOR   $
> 1.00 each

I use these for RF bypass protection for my NSTs. 
They might serve OK as tank capacitors in a small,
table top coil.  For a big Tesla coil (>500W) you
should consider an MMC or a bottle cap.

> 
> 3.  When demonstrating a coil indoors what do you
> use for a ground?  Do
> you simply run a wire to outside?

Use a ground rod or a buried copper pipe.

> 
> 4.  Wouldn't a conical secondary be more efficient
> than a cylindrical
> one?  One reason being that the magnetic force from
> the lower wider part
> of the secondary coil would create a higher voltage
> on the smaller higher
> part.  Know what i'm saying?

Don't get coupling mixed up with efficiency.  When
discussing Tesla coils, the two are barely related. 
Tesla coils require loose coupling for proper (and
efficient) operation.  I know it doesn't seem logical,
but I assure you it is true.  Also, I think the
problems associated with finding a conical form and
winding it would outweigh any performance advantage. 
Every successful Tesla coil I've ever built or studied
used a "regular" cylindrical secondary.  If you're new
at this, then stay on the beaten path.

> 
> I think that's all for now.  Thanks,
> 
> 		-Josh B.
> 
Best of Luck,

Greg
www.angelfire-dot-com/ga3/tesla 


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