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Unread 31-03-2008, 14:29
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Re: witricity legality?

Quote:
Originally Posted by Al Skierkiewicz View Post
...unlicensed operation must be below 30 microvolts/meter at 30 meters from the radiator....the experimental device was described as transmitting 150 watts, in general it would have needed to be licensed even if only an experimental one.
The odd/nifty/novel thing about what's being called WiTricity here is that it's strictly a "near field" thing. There is no traditional radiative field; as the Wikipedia quote says, it involves "evanescant waves" which fall off exponentially with distance. I haven't seen rigorous mathematical details of the setup, but there are references to the receiving coil having to be within a quarter wave of the transmitter. At 10 MHz, 30 meters is one wavelength. It might be far enough for the field strength to be sufficiently low to not need a license.

But evanescent waves are still EM, and they still interact with any conductors within range -- and in doing so, they can scatter the energy so that it does radiate. Shadow has apparently picked up on a comment that the connection between the tuned coils is "mostly magnetic" and thus infers that it isn't radio, but fails to recognize that all the energy that is not transferred between the coils is going to interact with metal, ionic liquids, human flesh, etc. in the same way as any other RF energy.