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Re: [TCML] RF Ground and Brass
In a message dated 3/5/08 10:08:05 A.M. Eastern Standard Time,
>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
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
>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
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
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
Center for the Advanced Study of Ballistic Improbabilities
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