RE: Wireless Transmission

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Steve Conner" <steve.conner@xxxxxxxxxxx>

>In the end, I think established and
>resistant science beat Tesla down unjustly and the kinder pigeons he sat
>feeding were more worthy company

Well I'm not so sure. I have spent a lot of time reading the Colorado
Springs notes and any other material written by Tesla I could find. The
impression I got was that he was right out on the very edge of science at
the time and speculating away like crazy. He simply wrote down every thing
that crossed his mind. His lab notes were not meant for public consumption.

A lot of this stuff, like the non-Hertzian waves, sounds very compelling. I
am ashamed to admit I nearly built one of those caduceus coil things myself
:-o But I now believe the whole thing is a myth and in fact Tesla just
didn't understand how energy really is propagated by EM waves. (Probably
nobody did in 1899.)

I have had fun reading the CSN and trying to understand how he was thinking
at the time. As far as I can tell he thought the ground current from his
magnifier was driving the earth and ringing the whole globe like a big
spherical electrode. All the energy was transmitted through the ground while
the topload just acted as a "counterweight" or charge reservoir to let the
drive work.

He didn't seem to have a conception of what we now know as displacement
current. I ought to explain this further. Displacement current is the dD/dt
in Maxwell's curl B= J + dD/dt. In intuitive terms this equation says that a
current creates a loop of magnetic field around itself, and a time-varying
electric field creates a loop of magnetic field just like a current does,
even if there is no conductor present for any "ordinary" current to flow in.

This strange "current" that flows in thin air really exists. It explains how
radio waves propagate and why you can get RF burns from touching grounded
objects while running your Tesla coil. And also why your electric guitar
stops buzzing when you pick it up. Anyway. The modern model says that the
displacement current from the topload returns to ground and cancels out the
ground current. The current "lands" in a patch around the coil that is
called the "near field" or "reactive field" and practically no ground
current or radiation leaves this zone. Any EM that makes it out of the near
field propagates just as radio waves do, because it _is_ radio waves.

I have never seen any experiment done by anyone with a Tesla coil that would
deny this modern explanation. The near field was probably several miles
across with Tesla's big transmitter and I suppose he radiated a fair amount
of power in the far field too, with that huge antenna mast.


Steve C.