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Re: RF biological hazards? (fwd)



---------- Forwarded message ----------
Date: Tue, 5 May 1998 16:22:09 -0700
From: Jim Lux <jimlux-at-earthlink-dot-net>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: RF biological hazards? (fwd)


> 
> ---------- Forwarded message ----------
> Date: Wed, 6 May 1998 09:15:22 +1200
> From: Malcolm Watts <MALCOLM-at-directorate.wnp.ac.nz>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: Re: RF biological hazards? (fwd)
> 
>      RF output is not continuous. It is a series of damped rings 
> occurring at a frequency well below where the skin effect would come 
> into play i.e. the repetition rate is << than the resonant frequency. 
> This particular hazard doesn't exist with a CW run coil but that 
> doesn't preclude penetrating burns in nervous tissue etc.

The low duty cycle applies for thermal effects, but does it apply for other
effects. There is also an interesting phenomenon with microwave pulses
where the rapid heating of ear tissues causes audible clicks, even at very
low average powers, but high peak powers (watts/square meter)

> 
>     IMO the best way to ascertain whether a shock hazard exists is to 
> look at primary energy (Joules).
I agree.. Leaving aside long term effects of E fields, etc., it is the
stored energy that gets dumped into you that is the key thing. A few joules
will hurt, but probably not injure.

 The other thing is that if you 
> connect with streamers at the farthest distance you can, some
> rectification appears to be occurring and you can get very
> substantial shocks, even with a very low primary energy.

There is also the arc to the power line problem, also, as mentioned by
Greg. A good reason to not ground yourself with a low impedance ground!!!
(No sweaty bare feet in the rain!) Here is a question, assume that you have
this low impedance arc between the TC and you. Do you also get an arc from
you to the ground, or is the power just coupled capacitively? In the latter
case, you wouldn't be part of a power arc.

BTW, this is why your antistatic grounding strap has a 1 Meg resistor in
series. It is grounded enough to bleed the charge off, but not enough to
provide a low impedance ground if you should accidentally come in contact
with line current. The resistor also limits the discharge current if you
touch a charged component.