Re: HF sparks
From: John H. Couture[SMTP:couturejh-at-worldnet.att-dot-net]
Sent: Tuesday, August 05, 1997 2:48 AM
To: Tesla List
Subject: Re: HF sparks
At 05:24 AM 8/3/97 +0000, you wrote:
>From: Peter Electric[SMTP:elekessy-at-macquarie.matra-dot-com.au]
>Reply To: elekessy-at-macquarie.matra-dot-com.au
>Sent: Saturday, August 02, 1997 5:34 AM
>To: Tesla List
>Subject: Re: HF sparks
>Tesla List wrote:
>According to the WinTesla program, my coil is already running at around
>this freq ~ 320Khz with my approx 18Pf toroid (8" by 20") and 22" by
>3.5" secondary with 840 turns 22# wire. These parameters result in 30"
>max sparks. I will try the old led/signal generator trick to see if this
>is right but maybe you can plug these values into your magic program and
>see if it agrees.
>I have done some experiments substituting a 22" sphere for the toroid
>(around 30pf by my estimation) and the primary tuning changed
>considerably (8 turns to 11 turns) so I gather the freq would have
>dropped by at least 20%. The result was an increase in spark length to
>33" but the sparks were harder to control i.e. they mostly struck the
>strike rail on the primary or the ceiling.
>All of this still leads me to believe that lower freq. and/or greater
>secondary capacitance still gives you longer spark, but I am open to
>Cheers, Peter E.
The JHCTES computer program shows 331 KHZ for your coil. This is found
from the pri and sec LC circuits. These two circuits must be in tune and
give equal frequencies. The program shows 8.9 sec inductance and 25.93 pf
sec capacitance. What does the WinTesla program show?
With the 22 inch sphere the frequency should be about 274 KHZ. You
indicate a capacity of 30 pf, however, the capacity will depend on the
proximity to the coil, etc which lowers the sphere capacity and increases
the frequency. The test frequency could be higher than 274.
Changing the toroid or coil to something larger may increase the spark
length up to the maximum capability of the power source. Note that optimum
parameters for spark length vs power, frequency, Q factor, K factor etc,etc.
are now found by trial and error. Computer programs eliminate some of the
guesswork. Improvements will depend on how well coilers test their programs
in the future to get new accurate data. There are few coilers who do much
testing that produces tabular data and graphs upon which to base design
Many people on the T. List misinterpreted my reference to increasing the
frequency as increasing the spark length. I was thinking of sine waves and
energy. Normally we think of the frequency reducing to DC. However, if you
have an oscilloscope and sine wave generator it becomes obvious that as you
lower the frequency the amplitude of the sine wave takes longer to rise
and would eventually approach zero and zero energy at an infinitely low
frequency. Increasing the frequency would represent an increase in energy.
Reducing the frequency of a sine wave does not go eventually into DC but to
zero amplitude and energy.