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RE: [TCML] RF Ground and Brass
Hi Phil,
As I should have stated, I have not personally run my coil without a secondary base connection, and it's not something that would be a good idea to try! There is a danger in blindly repeating things heard, though I thought I've heard it from multiple sources. I agree that you would effectively have a bipolar coil. Perhaps the results may depend upon how close the primary coil is to the secondary base, determining whether or not there would be arcing there. It does seem a little hard to swallow that disconnecting the base would show NO difference in performance and no extraneous arcing.
There is a capacitive path between the secondary base and the primary. If there is a poor direct path from the secondary base to RF ground, the capacitive path to the primary, NST, and ultimately to the mains will be used. The quality of one's RF ground is a continuum; if one has a "perfect" ground connection to the secondary base, then there would be no current in the capacitive path. If one has a "pretty good" RF ground, the secondary base voltage will still be non-zero and there will be some capacitive coupling to the primary, NST, and mains. The worse the quality of the RF ground, the more coupling will occur to the primary and out to the mains.
Unfortunately, no one has devised a means of quantifying how much RF gets coupled into the mains, so everyone (myself included) simply reports "I use X ground rods and Y cable and it works just fine".
You have inspired me to do some experiments. With my 4/20 NST-powered mini coil, I'll try various secondary base connections, ranging from no connection (if it doesn't arc), to a long and lazy piece of #42AWG lying insulated above the basement floor, to a copper ribbon tied to the water main in my basement. I'll report maximum spark length; unfortunately I have no means to gauge mains hash. This will be interesting - I don't recall ever hearing of such an experiment!!
Regards, Gary Lau
MA, USA
> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of FIFTYGUY@xxxxxxx
> Sent: Wednesday, March 05, 2008 10:14 PM
> To: tesla@xxxxxxxxxx
> Subject: Re: [TCML] RF Ground and Brass
>
>
>
> In a message dated 3/5/08 10:08:05 A.M. Eastern Standard Time,
> Gary.Lau@xxxxxx writes:
>
> >Your point about the wire not getting warm if it represents a high RF
> impedance is well taken, but I
> >don't agree that gauging ground conductor suitability by spark performance
> is valid. Many coilers
> >have noted that performance is unaffected even when they accidentally
> forget to connect the
> >secondary base to anything.
>
> I'd have to strongly disagree with that statement, based on recent
> experience!
> I had incredibly hot primary-to-secondary arcing at the base of my 6"
> SISG coil until I connected the secondary base to earth (via a length of 10ga
> stranded THHN). At first I thought it was the primary arcing to the secondary,
> until I realized it was the floating secondary arcing to the primary!
> Without grounding the base of the secondary somehow, you've got a
> bipolar coil!
>
> >The consequence of having a good or bad RF ground connection is not
> variable performance. It only >affects how much RF gets coupled into your power
> mains.
>
> I don't see where grounding the secondary or not affects the power mains
> in any way. The issue is whether the return current for the secondary has a
> sufficiently low impedance path to follow that the secondary current will
> *tend* to not travel on the power mains.
> No matter how wonderful your RF ground is, if you get a secondary strike
> directly to your house wiring you're gonna have a problem.
> The rest of the noise is coming back from the primary or the power
> supply wiring. Secondary grounding doesn't matter for this, but the quality of the
> RF ground that the Terry Filter, shielding, EMI filter, NST/PIG/whatever is
> attached to would have an effect.
> None of this considers radiated RF from the secondary, primary, spark
> gap or power supply. Neither does it consider the induced voltages from the
> strong E and M fields near the prim/secondary.
>
> > In the absence of a good RF ground connection, the only other path to
> ground is through the power
> >lines.
>
>
>
> All that secondary capacitance has an effective return path of "everything
> in the near vicinity". Grounding your secondary doesn't affect it's
> capacitance change due to the proximity of walls, ceiling, and the floor!
>
> >That's what makes the topic of "proper RF grounding" so difficult to
> resolve. There is no known
> >means of gauging success or quality.
>
>
>
>
> Your statement implies that grounding the secondary has *no* perceivable
> effect. Otherwise, it would be measurable. If you can cause a detectable change
> in quality, then improve it until you hit whatever point of "too expensive"
> or "too much effort" suits you. FWIW, I think that for practical purposes, we
> hit that point of diminishing return very quickly and easily.
>
> You have to admit, running a piece of 18-10ga wire to a desired RF
> ground is such a cheap and easy thing to do that there's really no good reason not
> to.
>
> -Phil LaBudde
> Center for the Advanced Study of Ballistic Improbabilities
>
>
>
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