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Re:Humid atmosphere

Hi Paul,
        Thanks for posting the spec. on your coil.

> The coil is wound on a 5ft 8" high polyetheleyne sewer pipe of 2ft
> diameter. Primary is a flat 2mm thick 3inch wide copper strip wound
> ten times at 1/2inch spacing. The output terminal is a tin cooking
> pot. The round bottom Indian type pots used for catering purposes
> which has a diameter of 22inches. (It was the biggest they make and
> only cost $15 US.) The spark gap is a variable speed rotary gap.
> Capacitor is 0.1mfd. The secondary resonant frequency, measured by
> connecting the frequency generator through a 1k resistor to the
> base of the secondary and measuring from the base to ground with
> the oscilloscope, was around 85Khz when I was alone.

First comment - you too would have been influencing the machine. I 
just posted on measuring. I'd suggest that while the 1k resistor isn't
causing a huge amount of inaccuracy, it will certainly be causing 
some. I guess the point is: you wouldn't even think of operating the 
coil with 1K in series with ground. Is the coil normally well 
grounded?

> I did not understand the changes on the oscilloscope when the
> second body approached. First the trace goes to the frequency of
> the signal generator, then as the body gets nearer a second trace
> appears, inbetween the first as if the frequency has doubled. (Is
> this possibly a higher harmonic frequency of the original?)

I'm almost convinced that your grounding is poor. A 1k resistor in
series with the coil is certainly not equivalent to grounding the
secondary well. A poorly earthed coil can be excited in a number of 
resonant modes. It is obvious that your system does not have a narrow
bandwidth, and just reading the next part of your post suggests why
that might be....

> It is not stable and varies in frequency but not amplitude.  After
> that there are many traces visable at about 15 ft and I could not
> even tell which was the original or if it was even still there. The
> scope can go up to 3Mhz but still read multiple criss cross lines
> no matter what frequency you fed in from the signal generator. As
> the body moves away the reverse happens and the resonance returns
> to the original frequency. The coil was standing on a 4ft high
> wooden stage about 20ft square and a 10ft high grounded wire fence
> was around the outer edge of the stage to protect the coil from
> the visitors. The body was outside the grounded wire fence.

Try either removing the fence or putting a gap in the wires so they
don't form a series of shorted turns.

> After reading what I have just written it is clear I have missed 
> something as none of it makes any sense. I assumed it was the high 
> conductivity of the air causing the problem but it may be something 
> as simple as the damp wooden stage conducting from the base of 
> the secondary to the cage. I never did find the problem and I 
> have tried the baby coil (14") in the jungle conditions but still 
> get greatly reduced arcs, (4 inches) which increase in length in 
> the towns air conditioned trade centre.

My personal experience re humid air has been much the same as yours,
but others have found the opposite. I guess finding out why your
tuning is so bad is the real goal.

<snip>
     Do the touch switches rely on the "toucher" coupling some stray 
signal in to activate them? You kight look at stray signal variations
(e.g. heavy/light use of power in the building at odd times). Also,
skin dampness might be a factor.
    I'm sure you'll get it working eventually.

Keep trying,
Malcolm