Re: self-C comments

Hi Richard, all,
                 Thanks for a great post. 

> 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.