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Re: Can I touch?
Bill Walker, All,
Bert Hickman has written an excellent post below on the subject of hazards in
body contact with high frequency high voltage sparks. I have on several
occasions personally experienced a deep aching in my hand as though I had been
pulverizing it with a meat tenderizer, only a much weaker pain, after letting
20 inch streamers from a vac tube TC outputting about 1 kW of CW RF contact a
metal object grasped in my hand, and also some direct spark to skin demos.
Clearly there is deep nerve damage occurring. The discomfort comes on within a
minute or two after the exposure and lasts a long time. I don't do this nearly
as often anymore. As far as letting myself be hit with the discharge of a
disruptive TC, I make every attempt to insure that I don't.
Robert W. Stephens
Director
AREA31 Research Facility
<http://www.area31-dot-org>www.area31-dot-org
Bill,
Good.... While the output from low-power vacuum tube CW coils is
probably harmless, larger-power tube coils can deliver sigificant output
current, and the danger with this is two-fold. First, if you let the
sparks directly hit your skin, the "entry points" are actually little
burned puncture holes, the surrounding tissue is actually charred, and
the smell of burning flesh can permeate the air. As long as you keep the
sparks moving, little permanent damage will be done. Taking a sustained
arc in one place will create a nasty, slow-healing RF burn. Secondly,
letting the sparks hit a piece of metal in your hand will prevent the
above external burns, but the RF current STILL tends to flow _through_
your nervous system and blood vessels.
"Skin effect" does NOT protect your body - at 100 kHz the skin depth of
your body is about 39 inches! Make no mistake here - TC RF currents
flow THROUGH your body, not on the surface or through your skin. Your
skin, in fact, is a relatively poor conductor compared to your mervous
system, blood vessels, and major organs. Compounding this, your body's
pain sensors do NOT provide you with any warning that you may be
slow-cooking your innards. And, the higher the coil's power, the more
risky this behavior becomes. Symptoms of nerve or tissue damage include
dull pain or aches in the muscles or joints (sometimes hours later), or
tingling or numbness that (usually) goes away with time.
Unlike a Tube Coil, a discharge from a disruptive (spark-gap) coil will
almost always give you some sensation of electrical shock. This ranges
from barely noticable in small coils to body-convulsing potentially
_fatal_ jolts off larger systems. The higher peak power levels, combined
with the typically large topload capacitance mean that higher peak
output voltages are produced. And, when you take a hit off a
medium-sized system, it's NOT an RF discharge. Instead, it's more like a
HV capacitor discharge going through your body, and the peak current can
easily be in the ampere range if the discharge arcs from you to ground!
You don't want to be on the receiving end of 200-300 kV hit from a
charged 30-50 uF topload/coil capacitance - at best it'll really rattle
your teeth, and the resulting muscle contractions may cause further
injury.
If you still feel you must try this, keep your power levels low (close
down your main spark-gap), stick will a small coil, stand on a well
insulated platform so that you're NOT grounded, and have a trusted
associate control power to the coil. Most experienced coilers avoid this
practice...
Safe coiling and happy holidays to you!
-- Bert --