Re: self-C comments
Richard Craven said:
>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.
<another big snip of interesting text>
I have not built a conical coil, but have looked at it
mathematically. I would expect it to be rather disappointing as a
conventional tesla coil. The large conical base is where most of the
inductance of the coil is (and most of the wire length), and, as a result,
the coupling is rather high there unless the coil is moved away from the
primary. From a VSWR standpoint, the voltage rise is approximately 1/4 wave
sinusoidal along the length of the wire. Since most of the wire length is
near the base, most of the voltage rise is also there. This yields
increased self capacitance in this vicinity, since the turn-to-turn voltage
is significant there. The top turns of the coil provide little inductance,
little wire length, and reduce the total inductance of the coil compared to
a solenoidal design with the same total wire length, because the flux lines
from fewer turns contribute to the total inductance.
I know Richard Hull and others have built these coils. Perhaps we
can get some practical experience from them as well.
Mark S. Rzeszotarski, Ph.D.