Re: RF biological hazards? (fwd)

---------- Forwarded message ----------
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)


Just a comment on the skin effect:

>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)
>> 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)

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