Re: Tesla Coil RF Transmitter

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 10:12 AM 9/17/2005, you wrote:
> Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx>
>
> Tesla list wrote:
>
> > Original poster: stork <stork@xxxxxxxxxxxxxxxxxxx>
> > Thank you Jim!
> > Electrometers are designed to ONLY detect electrostatic 
> > fields.  They cannot and do not detect magnetic fields.  This is 
> > the very point of this whole thread.  This is a time varying 
> > electric field without an associated magnetic field.  The 
> > transmitter and receiver are longitudinal and non 
> > Hertzian.  Electrometer probes oriented perpendicular to E field 
> > lines capture the radiated E field. The arrangement receives only 
> > longitudinal E field radiation.  Experiments bear this out, it's 
> > not "proven" by some convoluted theory.
>
> This "longitudinal" field is a "local" field in antenna theory. It
> decreases to practically zero at quite short distance.

In fact, where the "local field" is exactly equal to the "radiated 
field" is the boundary between "near" and "far fields".  Caution, 
there are other definitions of far field around: e.g. where the plane 
wave approximation is valid to some level of precision (2d^2/lambda 
is a common "far field" distance and corresponds roughly to the 
wavefront being flat enough that a uniformly illuminated circular 
aperture is diffraction limited)

I personally prefer the term "reactive near field" to indicate that 
energy is being stored in the field and might be returned to the 
physical object (n.b. the field around a TC is clearly in this 
category).  In the "radiated far field", no energy is stored, it's 
just propagating away.