Re: Tesla Coil RF Transmitter

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Steve Conner <steve@xxxxxxxxxxxx>

I was thinking some more about this wireless energy
transmission thing and an interesting thought struck
me. Well it was interesting to me at least :-/

Tesla's wireless power concept was- as far as I know-
based around the idea of creating "Terrestrial
stationary waves". That is, standing waves whose nodes
and antinodes are always in the same points on the
earth's surface.

But! Is it not the case that a standing wave can't
transmit power, by definition? According to the usual
analysis, a standing wave is the sum of two travelling
waves of equal magnitude but going in opposite
directions. So surely any power carried one way by one
wave would be carried straight back by the other wave
and the net power would be zero.

As far as I understand, a standing EM wave has its E
and H components 90 degrees out of phase, so the
energy just oscillates between electric and magnetic
forms rather than going anywhere. In this sense it is
the fields equivalent of reactive power in circuits.

It wasn't till after Tesla's time that radio engineers
realised the travelling waves are what do all the work
and the standing waves just increase losses by causing
higher voltages and currents than if the travelling
wave were present on its own. It's standard practice
to tune radio antennas by measuring standing wave
ratio (SWR) in the feeder system and adjusting for the
best figure.

I'm not sure how you would go about calculating SWR in
a power transmission system made from two Tesla coils.
But I bet it is pretty high since there are huge
amounts of reactive power flying around.

Steve Conner
http://www.scopeboy.com/