a phase displacement of 90 degrees exists
the wave of charge potentials induced by an alternating current
signal upon the water ... and the resulting wave of charge displacements
occurring in the water body between the segments.17
The method of propagation, then, is to periodically
alternate electrical charges on the two plates that will launch
sinusoidal carrier waves into the medium. When one plate is positive,
the other will be negative; then the first will be negative and
the second positive. This action, the patent states, will create
the sinusoidal waves.
In a detailed
analysis of forces involved in this type of transmission Curry
shows that radiators with a capacitance of .0053 microfarads operating
at 100 kHz with signal generator output of 200 volts coupled with
a biasing potential of 1000 volts will produce a force from its
charge displacement of 26,500 dynes.18
On the receiving
side, Curry states that the charge gradient can be expected to
attenuate substantially at even moderate distance from the point
of transmission. As an
example he notes that if a signal intensity of 10,600 dynes at
the point of transmission is reduced one billion times the "standing
wave of the signal energy will therefore be charged with a force
differential of 1.06 x 10-5 dynes. Each dipole in his
example has a capacitance of .0053 microfarads with a system capacitance
of .00265 microfarads. The
voltage developed in the receiving network is .02 volts. As noted "this is substantially above
the minimum requirements of signal intensity for the detection
of electrical signal energies."19
detailed analysis, however, overlooks the important point that
electrostatic waves do not propagate into the medium in the same
way as electromagnetic waves. In an electromagnetic transmission
system, charge is accelerated in an elevated conductor, an antenna,
to launch waves omnidirectionally into
the air. At a receiver, the electromagnetic waves induce a current
in the antenna. The variations in the current are processed by
the detection circuitry to replicate the transmitted information.
In electrostatics, it is not necessary for
flux lines to detach from an antenna and close upon themselves
to propagate a wave that is received at a distant point.
The transmitter, in Tesla's plan, oscillates the earth's
charge and the receiver is connected to that same charge reservoir. Signals are not launched, but exist as pressure
variations in the earth's oscillating electric field. Because
the field already exists at the point of transmission and at the
point of reception, the propagation characteristics are different
from electromagnetic waves.
In addition to the mode of propagation being different, what travels
between the transmitter and receiver is different. In electromagnetic transmission waves are
sent out that are picked up by the receiving antenna. These waves
induce a current the antenna.
In an electrostatic system a current passes directly between
the transmitter and receiver.
This current is the same as that which exists in a capacitor, that is,
it is a displacement current.
In a standard inductor-capacitor-resistance circuit, when
it is energized and oscillating, it is understood that the current
that passes through the conductors is completed through the non-conductor
of the capacitor's dielectric through a displacement current.
As charge is changed on one plate of the capacitor, an
opposite but equal change in charge is seen on the other plate
of the capacitor. In Tesla's system the transmitter and receiver
act as the capacitor plates and what passes between them is a
Displacement current, today, is seen as something of a virtual current,
something different from a "real" or conduction current
that flows through a wire. Tesla,
however, understood what is meant by an electrical current in
the same sense as Maxwell - that "all charge is the residual
effect of the polarization of the dielectric"20
and that "the variations of electric displacement evidently
constitute electric currents."21
As a Maxwellian, Tesla was correct in describing his transmission
system as one using true electric currents.
Tesla's wireless electrical energy
transmission system differed in all three characteristics he claimed
- it was
not electromagnetic, it operated through the earth or water, and
conveyed electrical energy by a current.
Once Tesla's communication method is better understood
as a new branch of electrical science that was started over 100
years ago, it will not only have an impact on terrestrial technology,
but will have applications in the future for space communications.