[RFI] wireless power at 6.4 MHz?

David Robbins K1TTT k1ttt at arrl.net
Fri Nov 17 09:31:02 EST 2006

Induction without a ferromagnetic material to contain the flux still results
in a magnetic field in the air, and where there is a changing magnetic field
there will be an electric field and therefore radiation.  It obviously won't
be efficient if they keep the transmitter antenna small, but then again, as
implied by your statement about the quicker decay of the field, the
inductive transfer will be even less efficient.  So like any small magnetic
loop antenna or any other small coil, it will 'radiate'.

Personally I think the charging 'pad' concept is much better, at least there
you can closely couple to a pickup coil which should reduce the radiation
quite a bit.  

David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net

> -----Original Message-----
> From: Richard (Rick) Karlquist [mailto:richard at karlquist.com]
> Sent: Friday, November 17, 2006 04:19
> To: k1ttt at arrl.net; rfi at contesting.com
> Subject: RE: [RFI] wireless power at 6.4 MHz?
> Radiation is not essential.  You can transfer power by induction.
> In fact, the article cited states that it works by induction.
> Induction is not radiation.  It decays faster than the inverse
> square law.  This is called evanescence.
> Rick N6RK
> > It has to radiate or no power can be transferred.  From their
> description
> > its either another EH antenna like scheme or an interesting theoretical
> > piece of work with no practical application.
> >
> >
> > David Robbins K1TTT
> >

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