I think an important aspect that is being overlooked is the effect the RF envelope has on pain perception. While it is true that nerves cannot respond to AC signals above 40KHz or so, the break rates of discontinuous wave TCs is almost always far, far below this level. It is entirely possible for nerves to feel pain and have their conduction disrupted as a result of the low frequency pulsing of the RF envelope caused by the interrupter in solid and vacuum state coils, and spark gap in traditional coils. Each beat of the RF envelope acts upon the nerve the way a DC pulse would. Even with a CW SSTC/VTTC coil if one holds their hand or handheld conductor far enough away from the discharge that discontinuous arcing to the object or their hand occurs this too imposes a detectable sensation in the nerves. TENS electroneural stimulation devices apply significant fractions of an amp of AC or DC at 50-150V (using a wet conductive electrode on the skin) at rates between tens of Hz and several hundred Hz (the same frequencies as TC interrupters and spark gaps!) and the application is often focused explicitly at the joints. The intensity of the pulses is intended to be adjusted to just below the pain threshold, but just above the point where sensation is observed. Many practitioners and doctors recommend all day every day application for the most serious patients. Surely if any are to suffer nerve damage it would be those who apply 300mA @ 100V @ 120Hz (average power TENS unit adjusted to the midpoint) directly across a joint for 16hrs a day, seven days a week!
As for the actual danger of the RF itself one has to initially separate the effect of the RF from the effect of the low frequency pulsing(when not running CW). There is a LOT of data on RF exposure limits, and in all of it - it is the thermal aspects which cause damage to tissues. Others have brought up the various pain relieving electrotherapy and diathermy uses in the medical field and accidental electrical shock data for good reason; heating effects aside the current imposed on the nerves from RF does not appear to have any significant effect from a medical standpoint. Now, if the exposure limits are exceeded then damage can be done AND the victim may not be aware of it at the time as certain areas of the body have poor innervation or pain localization in the brain.
If we’re going to include anecdotal evidence:
I have a lot of experience using gas discharge tubes with CW solid state coils, and while I am always careful to greatly limit direct arcing exposure (mostly for burn prevention, but the pulsing envelope is painful!), I have never been afraid to conduct large capacitively-coupled currents through my extremities and body while enjoying a discharge tube. I have even noted pain relief from the associated diathermy when I had injured my hand. These aren’t wimpy 100W SSTCs either, my largest coil runs 3100W CW with more than 100mA of topload current!
If there is any nerve-centric non-thermal damage being done then I find it likely the result of the low frequency pulsing of discontinuous tesla coil output, and not of the RF itself. One can postulate it is similar to the long lingering nerve pain from excessive vibration exposure that workers experience. By the way, the treatment for such is prescription of a TENS unit!
Sincerely,
Matt Sig Giordano
www.SigurthrEnterprises.com
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