Re: Tesla Coil RF Transmitter

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Paul Nicholson <paul@xxxxxxxxxxxxxxxxxxx>

Gary Peterson wrote:

> 1.2 ... In the case of this type transmitter, the transfer of
> electrical energy is between the two ground terminals in the
> form of true conduction currents, and also between the elevated
> terminals.

This is a radio wave by another name.  'true conduction current'
doesn't offer an alternative to EM waves for transferring energy.
There is only one type of current in electrical engineering, and
it always requires a field to drive it.  A current is a flow of
charge (usually electrons) and they are driven along by a field.

There are no grounds for believing that inefficient radiators such
as described by Gary will mysteriously force out ground currents
without projecting a field the same distance.  Any such suggestion
is completely contrary to the known laws of nature.

As you reduce the height of the TC topload to a small fraction of
a wavelength, the resonator becomes a poor radiator of EM fields.
They become more confined to the vicinity of the resonator - and
so do the induced currents in the ground!

There is no such thing as 'true conduction current' to come and
rescue the situation by propagating current without a field.

Attempts to revive Tesla's ideas for broadcasting power, by
introducing concepts such as:- cavity resonance using ionosphere
or artificial plasma layer, projecting Zenneck waves, etc,
are simply providing one mechanism or another to allow the field to
propagate further, and thus allow current to be 'transmitted'.
Really, it is always the field that is causing excitation of
current in the receiver.

A receiving TC tuned to the same frequency as a transmitting
coil will receive well, but only to the extent that the
transmitting coil broadcasts its field.  As the coils are moved
further apart, the coupling coefficient drops very rapidly.
You may try to mitigate that by demanding higher and higher Q
factors, but it is the loaded Q that must rise, and of course this
means that you cannot apply much load to the receiving coil.  This
relates to the fact that the receiving coil can, at most, only
make available the power that it can 'capture' from the field,
by virtue of its physical size in relation to the free space
wavelength.   It matters little if the two TC ground terminals
are joined together or not by a common 'earth'.

The best method for transmitting power by EM waves is to guide it
to its destination, using a waveguide, a coax, or as in most cases,
a pair of wires - such as a mains cable.  This is the efficient
and reliable system we already use: a system of guided waves
operating at 50 or 60Hz called a national grid.

The bottom line is - there's no magic way to excite a current at
the receiver without projecting a field to the receiver.  Even if
you make a current by shovelling charge into a lorry (truck!) and
drive it to the receiver, I will show that the energy conveyed is
represented by the EM field of that charge.  (In such a case, the
work of the lorry goes into the field as it has to drag the
load of charge away from the equal and opposite amount of charge
left behind at the transmitter.)

Dan (DUllfig@xxxxxxxxxxxxx) wrote:

> Tesla was transmitting energy by pumping a charge into the
> ground itself

The charge 'pumped' into the ground by the coil remains in the
vicinity of the transmitter.  It doesn't spread evenly over the
earth's surface, as I think Tesla had claimed it would.   Instead,
the charge is trying to return to the place (the topload and coil)
where it was taken from by the 'pump'.   So it hangs around the
transmitter, causing spectacular effects and warming up the ground
nearby.

Tesla never did transmit any useful amount of energy over any
worthwhile distance - except by using wires to guide an alternating
field out of Niagara Falls!

> why is it so hard for anyone to believe that Tesla was
> transmitting by conduction through the earth, and not propagation
> through the air?!

Because, really they are the same thing!!!   You show me a system
that is driving current through the earth, and I'll show you that
the fields which are driving that current are, in every respect,
an EM wave emitted by the transmitter.

Unfortunately, this is one of the cases in which nature just
doesn't work the way Tesla hoped it would.   There just is no such
thing as a 'true conduction current' capable of coupling two
TCs beyond the range of their mutual field coupling.
--
Paul Nicholson
--