Re: Lumped vs. Helical Re

Richard Craven wrote:
Malcolm and others,

It occurs to me that we expect the voltage to ground in the 
secondary to obey a sine distribution from base to top. What 
would be the effect of measuring the voltage in the 
secondary a few per cent of the way up and then 
extrapolating? This way you should be able to apply minimal 
loading to the coil ( the bottom of the coil is low Z so a 
high impedance resistive divider at this point would have 
little effect). It would be interesting to see the results 
of some measurements. At least here we are making use of the 
built-in voltage grading structure!

Richard Craven, England.

Hi Richard,

I would add one caveat to you first sentence. I think the 
secondary voltage distribution being sine-like is
certainly true for an ordinary transmission line where 
the only parameters are the inductance/length=const. and the
capacitance/length=const. But in a helix, the cap/length
is probably no a constant. Also, unlike the usual transmission
line analysis, there is a distributed mutual inductance term
in the equations....

Also, of course, even if we're talking about an ordinary
transmission line, the voltage distribution becomes linear
when the line is heavly loaded. I would imagine that most
tesla coils with large torriods approach linear voltage
distributions along their axis.

-Ed HArris