Re: SSTC Dangers - E Fields / Radiation

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <teslalist-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Dan,

On 11 Jun 2003, at 18:20, Tesla list wrote:

 > Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
<dhmccauley-at-spacecatlighting-dot-com>
 >
 > I know this has been discussed before, but the question really was never
 > assessed too well or answered.
 >
 > First the Facts:
 >
 > All of us who built SSTC coils know the field generated by them is very
 > strong, easily producing RF currents on anything metallic in the vicinity
 > producing strong RF burns when contacting
 > any of these metallic objects.
 >
 > Now the questions . . .
 >
 > 1.  Is the RF field generated by SSTCs much stronger (power for power) than
 > conventional tesla coils???  It would seem so, but then again, maybe we feel
 > safer around SSTCs and will more
 > readily approach them (closer) than when running similarily sized
 > conventional coils.

      Intuitively the strength of the field is dependent on the energy
residing in the resonator per cycle. One would have to compare a
particular coil of one type with a particular SSTC to quantify the
comparison.

 > 2.  How dangerous is this RF field??  If I can get scorching RF burns from
 > objects up to five feet away from my SSTC running (CW) mode, then the RF
 > field must be hazardous.  The question is,
 > how hazardous.  Will prolonged exposure (say a few minutes once a week
 > around these things cause significant tissue damage / cancer / etc...) over
 > a few years  ? ? ?

I don't think this has ever been quantified satisfactorily. I live
less than a mile from several AM transmitters operating on the
broadcast band, the most powerful of which is 50kW at a frequency of
567kHz. I have been there for 12 years at a duty cycle of
approximately 80% (I work elsewhere during the week) and have not
suffered ill health from it to my knowledge. I can extract useable
power (obviously not a huge amount but enough to light LEDs and run
low-power equipment) from the fields from the 10kW transmitter
operating at around 1MHz with a simple whip aerial approximately
twice the length of my body.

 > 3.  Nature of the RF field?  What exactly is the nature of this RF field?
 > The resonant frequency of the SSTC maybe around 150kHz to 300kHz, but is
 > this the predominant RF generated by the coil, or are the other higher
 > harmonics (way up into the MHz and beyond) created by the SSTC a large
 > factor in this field and thereby more dangerous?

The fields you are exposing yourself to are far higher since you can
draw sparks off nearby objects. However, every time I run a
moderately-sized disruptive coil, the peak field strength is probably
higher again although its difficult to know withouta comparative
measurement.

 > 4.  I did attempt to measure my coil using a NARDA RF sniffer, but the probe
 > end was geared more towards 300MHz up into the GHz range.  HOWEVER, at about
 > 6 feet distance I was getting number of 25-45 mW/cm^2 which to me is a lot.
 > However, this number was bounching around a bit, so I'm not sure if the
 > field was interfering with the probe.  But you would think the probe was
 > designed to withstand fields like this during measurement !
 >
 >
 > SSTCs are relatively a new thing on the block in the tesla community.  And
 > from just the proximity effects I'm witnessing (hair standing up, strong RF
 > burns off nearby objects, etc...) makes me think
 > these might be much more dangerous (in the terms of RF fields generated),
 > than conventional coils.  I think we really need to look into this much more
 > carefully.
 >
 > Any thoughts or comments ? ? ?

The same considerations would apply to any CW radiating device at
those frequencies, SS or not wouldn't it?

Malcolm