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RF biological hazards? (fwd)




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From:  Jim Lux [SMTP:jimlux-at-earthlink-dot-net]
Sent:  Thursday, May 07, 1998 12:33 PM
To:  Tesla List
Subject:  Re: RF biological hazards? (fwd)


> Date: Wed, 06 May 98 00:58:22 EDT
> From: Jim Monte <JDM95003-at-UCONNVM.UCONN.EDU>
> To: tesla-at-pupman-dot-com
> Subject: Re: RF biological hazards? (fwd)
> 
> 
> Hi,
> 
> Just a comment on the skin effect:
> <snip>
> 
> It seems like the skin effect will be about the same for both CW and
> non-CW.  The time-domain output of a non-CW coil would look pretty much
> like the product of a CW coil and a rectangular pulse with a low duty
> cycle.  So the corresponding spectral content of the non-CW coil
> would be the convolution of the CW coil spectrum with that of the
> rectangular pulse (a sinc function).  This convolution will spread
> the spectrum a bit (the lower the duty cycle, the greater the spread)
> but the energy should still be concentrated at the frequencies of the
> CW coil output.
> 
> Jim Monte

I was thinking that the waveshape might be more like an exponential pulse,
which would have a little wider sidebands, but, given the basic "prf" of
the TC being a few hundred hertz at most, even the 20th harmonic would
still be a few kHz.

I was more concerned about the difference between peak and average powers.
For instance, you could have a source with a peak power of 1 MW, and a 0.1%
duty cycle, for an average power of 1 kW. If there are any "threshold
effects" (like arcing in a void or cavity, or overcoming the "threshold" of
a neuron to fire it) then there is a big difference between the effects of
a high peak, low duty cycle signal and the CW signal, even though the
thermal heating would be the same.  I think this is referred to as
"athermal" effects of RF radiation, like the microwave auditory clicks
(although in that particular case, some think it is a short time scale
thermal effect).