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 

> 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.

     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,