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Re: High-Bandwidth Primary Circuit Behavior (fwd)



---------- Forwarded message ----------
Date: Thu, 30 Apr 1998 17:52:46 -0600
From: terryf-at-verinet-dot-com
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: High-Bandwidth Primary Circuit Behavior (fwd)

At 12:28 PM 4/30/98 -0600, you wrote:
>
>
>---------- Forwarded message ----------
>Date: Thu, 30 Apr 98 14:17:10 EDT
>From: Gary Lau <lau-at-hdecad.ENET.dec-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Re: High-Bandwidth Primary Circuit Behavior
>
>>I have written a paper on all this.  It is available in Word 97 formated
>>as an HTML web document at:
>>
>>http://www.peakpeak-dot-com/~terryf/tesla/experiments/experiments.html
>
>
>Terry,
>
>In your "New Model" of the primary circuit, you have the self capacitance of
>the primary inductor as 150 pF, measured by finding it's self resonance.
>
>I tried the same on my primary, 13 turns of .25" copper tubing, 15 degree
>saucer, ~6" ID.  I found the strongest resonance at 24MHz, suggesting a self-C
>of only 0.75 pF.  Considering my 4.25" x 22" secondary only has about 9 pF of
>self-C, I'd say 150 pF for a primary is way too high.
>
>There must be something else in your rig resonating at 1.2MHz.  I wonder what
>the ESL of the tank cap is and how to measure that?  But then, that wouldn't
>ring when the gap opens.  How about your (wire wound) protection resistors?
>
>Regards,
>Gary Lau
>Waltham, MA USA
>
>
Hi Gary,
        The linear coil I tested definitely has a strong resonance at
1.2MHz.  The test photos I gave probably did not show this effect well in
retrospect.  I have not tested my big flat coil yet for resonance.  If the
self C is much less for a flat (or cone) coil as you suggest it would be a
major find!  The point you and David Hall make about the inductance of the
10K resistors is very well taken.  I have done these test with a variety of
resistors but I never considered this inductance.  I don't think it was a
factor but I need to check this.

BTW the ferrite inductor shown in the paper has no turns on it and is out of
the circuit.  This is a future improvement that has not been wound yet.

        Terry