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Re: self-C comments
Hi Richard, all,
Thanks for a great post.
<snip>
> Bearing in mind erudite comments from Richard Hull (basically all the
> strays due to buildings floors and the like), has anyone any comments on
> conical constructions? I am not planning on building one, but it is an
> area of some interest.
I asked Mark Barton about the one he built once and he said that it
was so broadband you could pick a primary tap blindfolded and still
get sparks.
> Some may wonder why the capacitance of a secondary is unaffected by the
> dielectric coil form upon which the coil is wound. If we remember that
> the electric field of a TC extends outwards from the coil towards
> ground, it can be seen that the dielectric in which this field exists is
> air. If we put polyethylene inside the coil form, the electric field to
> ground is hardly modified. If we coat the wire we are using with a high
> permittivity dielectric, the percentage volume occupied compared with
> the air is also tiny so again the self-C is virtually unaffected ( I
> would guess we are looking at changes of a fraction of 1% and anyway
> these are swamped by extraneous C effects).
That mirrors my results with some poorly prepared PVC drainpipe (Q of
300+), but my failed "best coil" was would on polyethylene layers over
some ill-prepared formatube and came in with a Q which varied between
40 and 80 depending on air humidity.
<big snip>
Must study the rest of this post in detail. Much food for thought.
Regards,
Malcolm