Re: [TCML] Topload design questions

[bartb <bartb@xxxxxxxxxxxxxxxx>]

Hi Karl,

No problem. It's been done many times. A corona ring is really all 
that's required near the top turn when a toroid is raised relatively 
high, but a second and smaller toroid will perform the same function of 
the corona ring. Also, raising the toroid adds a few more pF to the top 
load C as compared to placement near the top turn (roughly 5pF per 10" 
of ht for a medium coils average 20 to 25pF top load) which is also a 
benefit from a slight energy storage view point (results in a little 
higher top volts needed for breakout).

Ed Sonderman (no longer on the list) had a 6" coil top loaded with a 
couple large in width toroids separated by a large aluminum cylinder 
between the two (about 20" diameter if memory serves). Looked wicked and 
was quite the "efficient" coil from a power vs. spark length aspect.

Take care,
Bart

Karl Thorkildsen wrote:
> First off, Hello!  I've been lurking for a while and have gained a 
> huge amount of knowledge by reading hundreds of posts here.  I have 
> built a couple of coils and am working on a third.  This will be run 
> off two 15/60 NST's.
>
> My question is about topload configurations.  I understand the need to 
> have a toroid in close proximity to the top of the secondary to avoid 
> corona discharge from the upper part of the primary.  But if using two 
> toroids, can the upper (and larger) toroid be elevated a few inches on 
> a conductive rod without adverse side effects?
>
> For instance in my case I'm considering a 6.5x30 inch secondary, with 
> a 3x12 and a 4x18 toroid and raising the 4x18 by 6 inches.
>
> Why, you might ask?  Well, I originally thought of this as a way to 
> reduce primary strikes, but I now realize this might only be valid 
> under certain conditions.  Another consideration is that it would look 
> cool.  But in the end I'm now just curious what the effect and 
> ramifications might be.
>
> Thoughts?
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