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A guide to some technical terms you'll encounter while reading about the genius of Nikola Tesla.

 This page was last updated on 03/22/13.


| A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |

absorption  A process that occurs as a radio wave passes from a dielectric medium into a conducting medium such as the earth or the ionosphere resulting in a loss of radiated energy.  (See Radio Wave Transmission and Absorption in the Ionosphere; Introduction to Wave Propagation, Transmission Lines, and Antennas .)

adiabatic plasma Part of plasma confinement system which involves particles where the orbit radius and orbit period are small compared to the characteristic scales of length and time.  In such plasma confinement the individual particles closely follow the magnetic field lines by tightly circling them.  The motion of these particles can be described by drift formalism and gyration centers.  On average, such plasma can be readily described by a well-defined theory--magnetohydrodynamics (MHD). [Source: Plasma Dictionary]

AC induction motor See induction motor.

aether, luminiferous  Literally translated, "light-bearing aether," a postulated material substance believed by early investigators to be the propagating medium of electromagnetic radiation.  The described properties were as follows:

Fluid in order to fill space;
Millions of times more rigid than steel in order to support the high frequencies of light waves;
Massless and without viscosity, otherwise it would visibly affect the orbits of planets;
Completely transparent;
Continuous at a very small scale.

 (See Wikipedia; see also ether.)

alternating current (AC) An electric current that reverses direction in a periodic manner.  Most electrical power systems generate ac with a frequency of 50 or 60 cycles per second.  See also polyphase AC.

alternator An electrical machine, usually rotary, for producing alternating currentSee also generator.

amplitude modulation (AM) A form of carrier wave modulation in which the amplitude of the carrier wave is varied in proportion to the amplitude of the modulating wave.  See also modulation.

anode A positively charged electrode that attracts free electrons or emits positive ions.  See also cathode.

antenna The part of a radio system that is designed to radiate radio waves into free space (or to receive them).  This does not include the transmission lines or waveguide to the radiator. 

antenna regions The distinction between electromagnetic fields far from, and those near to, the antenna.  The regions are usually classified into three zones; near (static) zone, intermediate (induction) zone and far zone, located by drawing spheres of different radii around the antenna.  The radii are approximately r < l for the near zone, r = l for the intermediate zone, and r > l for the far zone, with l being the wavelength () of the electromagnetic field produced by the antenna.  In the far zone, field components (E and H) lie transverse to the direction of the propagation, and the shape of the field pattern is independent of the radius at which it is taken.  In the near and intermediate zones, the field patterns are quite complicated, and the shape is, in general, a function of the radius and angular position (azimuth and elevation) in front of the antenna.  See also electromagnetic radiation, radiation fields, and slow-wave helical resonator.

American Wire Gauge (AWG) The AWG copper wire gauge is a logarithmic scale base on a wire's cross section, each 3-gauge step in size corresponding to either a doubling or halving of the area.  Note that the doubling of a wire's cross sectional area halves its' resistance.  In general a wire size gauge number corresponds to the number of operations involved in drawing a wire, a larger figure representing more operations resulting in a smaller diameter. 

arc An intense luminous discharge formed by the passage of an electric current across a space between two electrodes.  See also streamer.

asymmetric capacitor A capacitor the two plates of which differ in surface area.  Taken together, the elevated terminal of a magnifying transmitter and the earth comprise an asymmetric capacitor.

asymptote In analytic geometry, an asymptote of a curve is a line such that the distance between the curve and the line approaches zero as they tend to infinity. In some contexts, such as algebraic geometry, an asymptote is defined as a line which is tangent to a curve at infinity.[Source: ]

attenuation The decrease in magnitude of current, voltage, or power of a signal in transmission between two points.  May be expressed in decibels

audio transducer An electronic device that converts electrical signal variations to sound, such as a loud speaker, or sound to electrical variations, such as a microphone.  A bi-directional audio transducer is capable of conversion of sound both to and from electrical signal variations.

ballast A device for starting and regulating fluorescent and high intensity discharge lamps.

ball lightning An electrical discharge which takes the form of a luminous sphere.  In nature, the phenomenon is associated with thunderstorm activity.  It can also be produced by high voltage multiple-resonator Tesla oscillators. 

bandwidth A measure of the information carrying capacity, or size of a communication channel.  For an analog circuit, the bandwidth is the difference between the highest and lowest frequencies that a medium can transmit and is expressed in hertz (Hz). *

base band The frequency band occupied by information-bearing signals before combining with a carrier in the modulation process. *

beat (see CSN, p. 177)

beat frequency oscillator (BFO) Any oscillator whose output is intended to be mixed with another signal to produce a sum or difference beat frequency.  Used particularly in reception of continuous-wave transmissions. 

bremsstrahlung A German word meaning `slowing-down' or 'breaking' radiation.  The high-energy secondary X-ray emission produced when a fast charged particle such as an electron passes through matter.  The energy lost by the decelerating particle is emitted as electromagnetic radiation.  The primary particle might ultimately be absorbed while the resulting radiation can be highly penetrating.  Bremsstrahlung energy varies from 0 to the energy of the electron.

capacitor/condenser An electrical device that stores energy, consisting of two parallel conductors, usually metallic foil, insulated from each other by a dielectricSee also asymmetric capacitor.

capacitively coupled discharge plasma Plasma created by applying an oscillating, radio-frequency potential between 2 electrodes.  Energy is coupled into the plasma by collisions between the electrons and the oscillating plasma sheaths.  If the oscillation frequency is reduced, the discharge converts to a glow discharge.  [Source: Plasma Dictionary]

cart For large portable Tesla coils, the subassembly that includes the oscillator's primary coil, primary spark gap, (aka break, rotary break, circuit controller, or interrupter), primary capacitor, and possibly the high-voltage power supply transformer.

cathode A negatively charged electrode that emits free electrons or negative ions.  See also anode.

cathode reaction forces 

CEPT Conf—rence Europ—enne des Administrations des Postes et des T—lecommunications

charge A physical property, most often associated with matter, that gives rise to all electrical phenomena.  The basic unit of charge, usually denoted by e, is that on the proton or the electron; that on the proton is designated as positive (+e) and that on the electron is designated as negative (-e).  All other charged elementary particles have charges equal to +e, -e, or some whole number times one of these, with the exception of the quark, whose charge could be 1/3e or 2/3e.  Every charged particle is surrounded by an electric field of force such that it attracts any charge of opposite sign brought near it and repels any charge of like sign, the magnitude of this force being described by Coulomb's law.  This force is much stronger than the gravitational force between two particles and is responsible for holding protons and electrons together in atoms and for chemical bonding.  When equal numbers of protons and electrons are present, the atom is electrically neutral, and more generally, any physical system containing equal numbers of positive and negative charges is neutral.  Charge is a conserved quantity; the net electric charge in a closed physical system is constant.  Whenever charges are created, as in the decay of a neutron into a proton, an electron, and an antineutrino, equal amounts of positive and negative charge must be created.  Although charge is conserved, it can be transferred from one body to another.  Electric current, on which much of modern technology is dependent, is a flow of charge through a conductor.  Although current is usually treated as a continuous quantity, it actually consists of the transfer of millions of individual charges from atom to atom, typically by the transfer of electrons.  A precise description of the behavior of electric charge in crystals and in systems of atomic and molecular dimensions requires the use of the quantum theory. [Source: Fact Monster] See also space charge.  (See Wikipedia, Cheniere 1 and Cheniere 2.)  

charge displacement See dielectric displacement

coherent CW 

coherer A wireless detector that depends upon a phenomenon which can occur when there is a loose or imperfect electrical connection between two or more electrical conductors such as two oxidized copper rods lying one upon the other.  One form often used by Tesla is the metal filing coherer which typically consists of a short glass tube with two metal plugs fitted into its ends.  The space between the plugs is partially filled with course chips of an easily oxidized metal such as nickel.

cold plasma model A model of a plasma in which the temperature is neglected.  See plasma, thermal and nonthermal.  [Source: Plasma Dictionary]

Compton effect The increase in wavelength which occurs when X-ray photons with energies of around 0.5MeV to 3.5MeV interact with electrons in a material. First observed by Arthur Compton in 1923, it convinced physicists that light can behave as a stream of particles whose energy is proportional to the frequency. [Source: Wikipedia]


conductor Any medium capable of carrying an electrical current. 

conservation laws

continuous wave (CW) A sustained sinusoidal oscillation or oscillatory wave to which additional energy is added during each cycle.  Also known as an undamped wave.  A continuous wave can be modulated with audio, video or data.  A wave whose successive oscillations are, under steady-state conditions, identical.  When the wave is unmodulated the signal is highly monochromatic.  While the term is most commonly associated with the operation of non-spark type wireless transmitters, Tesla said he was able to produce "a perfectly continuous wave" with his more advanced disruptive discharge machines.  See also damped wave.

cord A type of copper wire made up of numerous thin strands in distinction from solid wire.  A common example is ordinary electrical lamp wire, also known as zip-cord.

core The center part of an inductor or transformer around which wire is wound.  Cores are typically composed of laminated steel, ferrite material, or a hollow dielectric tube, i.e., an air core. 

coulomb A unit of electric charge defined as the amount of charge that crosses a surface in 1 second when a current of 1 absolute ampere is flowing across the surface.  See international coulomb

counterpoise A wire or group of wires mounted close to ground, but insulated from ground, to form a low impedance, high capacitance path to ground.  Commonly used at medium frequency and high frequency to provide an effective ground for an antenna.  See also ground plane.

current The flow of electric charge

damped wave A "ringing" sinusoidal oscillation or oscillatory wave consisting of an initial pulse or peak followed by additional peaks of diminishing amplitude.  The term is commonly associated with the operation of spark-type wireless transmitters.  See also continuous wave.

dB See decibel

dBc Decibels referenced to the carrier signal. 

dBi Decibels referenced to an isotropic radiator.  (dBLi indicating linear isotropic radiator is sometimes used). 

dBm Decibels relative to 1 mW.  dBm is calculated by using the ratio of some power (expressed in mW) to 1 mW.  For example, 1 mW is 0 dBm and 10 mW is +10 dBm. 

dBsm Decibel referenced to one square meter. 

dBv / dB—v Decibels referenced to one volt or microvolt, i.e.  0 dBv is 1 volt or 120 dB—v. 

dBW / dB—W Decibels referenced to 1 watt or one microwatt, i.e.  0 dBW is 1 watt or 30 dBm or 60 dB—W. 

de Bro'glie wave a hypothetical wave associated with the motion of a particle of atomic or subatomic size that describes effects such as the diffraction of beams of particles by crystals. Also called matter wave. [Source: Fact Monster] (See Wolfram Research, )

decibel (dB) A dimensionless unit for expressing the ratio of two values of power, current, or voltage.  The number of decibels being equal to: dB = 10 log P2 / P1 = 20 log V2 / V1 = 20 log I2 / I1.  Normally, used for expressing transmission gains, losses, levels, and similar quantities.

demodulation The process of recovering a base band signal from a modulated carrier. See also modulation

detector A device or circuit for detecting the presence of propagating electrical energy of distant origin.  See also coherer

dielectric An insulating medium or one in which an electric field may be easily maintained.

dielectric displacement (D) Dielectric displacement is charge per surface area. When an electrical charge acts on a dielectric material, it stresses and polarizes the molecules in material. The material remains in an electrically stressed state when the charge is removed. [Source:

dielectric displacement current A mathematical construct developed by James Clark Maxwell to explain the apparent flow of electrical energy across the dielectric material between the plates of a capacitor.  [See also electrostatic induction and charge displacement]
     Dielectric displacement current is charge displacement without charge transport. Displacement current does not involve the motion of charges (current flow), but involves the formation of electric dipoles which create an effect similar to the movement of charges. Special case: The cyclical reversals of these dipoles gives rise to magnetic effects, which in turn gives rise to displacement currents. This alternating electro-magnetic cycle persists (propagates as light) until it is absorbed somewhere in time and space.
     Michael Faraday (1791-1867) formulated the concept of dielectric displacement to explain the residual electrically-stressed state of a dielectric material which had been exposed to a charge. James Clerk Maxwell (1831-1879) formalized this concept mathematically to explain capacitance and, in the special case, recognized that it could be the vehicle by which electro-magnetic energy moved. He went on to link this mechanism to light and calculated the speed of light from electric and magnetic measurements. He also postulated that forms of electro-magnetic radiation other than light existed. Heinrich Hertz(1857-1894) was able to demonstrate this about twenty years later by generating and receiving radio waves. [Source:

dielectric tensor The tensor describing the three-dimensional plasma response to three-dimensional electric fields; see (e.g.) Stix, Thomas Howard.  Waves in Plasmas, American Institute of Physics, New York, 1992 for details.  [Source: Plasma Dictionary]

direct current (DC) An electric current that flows in one direction only.  See also Kirchoff's Laws.

displacement current A mathematical tool used to account for the experimentally discovered fact that electric charges exert forces on each other over a distance. The concept of displacement current was developed by James Clark Maxwell. In a basic RC alternating current closed loop circuit, 1. Displacement currents are always time varying and never DC; 2. Displacement currents only occur in insulators or dielectrics. They occur only in circuit elements like capacitors, never in conductors of the circuit. That's conduction current and has a measurable magnetic field; 3. They are in closed loop circuits and are the same frequency, amplitude and direction as conduction currents. They usually have nearly the same phase as their antecedent conduction current, but some phase lag is always introduced by the capacitor itself. They are not tiny little currents and just hard to find. They are as big as the conduction currents.  Electrons don't mediate displacement currents. Electromagnetics governs current flow in the conductor up to the capacitor, then "current" becomes an electrodynamic event in the dielectric, and finally current again becomes an EM event in the conductor on the other side of the capacitor. Maxwell—s equation curl H=J+dD/dt suggests that displacement currents (dD/dt) create loops of H-field just as if they were conduction currents (J). Indeed this is the argument for how radio waves propagate, with H-fields turning into E-fields and back again as they fly along.  Maxwell's displacement current idea is unique in that it is probably not quite right, but somewhat difficult to prove wrong. The equations simply work for most cases.

disruptive discharge coil A Tesla oscillator which incorporates some form of spark gap switching device to discharge the primary capacitor(s) through the primary inductor.  See also Tesla coil.

distributed capacitance See internal capacitance.

drift waves Plasma oscillations arising in the presence of density gradients, such as at the plasma's surface.  [Source: Plasma Dictionary]

downconverter A device which provides frequency conversion to a lower frequency. 

dyne The unit of force equal to the force which accelerates a mass of 1 gram at a rate of 1 cm/sec-2. 

E x B drift Single-particle drift motion (see entry) which arises from crossed electric and magnetic fields.  [Source: Plasma Dictionary]

E-field see electric field

E-field probe a short antenna with a coaxial cable lead, used for the detection of high impedance E-field source signals over a very short range.  It is used in conjunction with an RF field/signal strength meter or spectrum analyzer.

earth resonance A theory stating that Earth possesses the properties of a massive LC circuit and can be resonated with a sufficiently powerful, properly tuned, grounded electrical oscillator.  An ability to electrically resonate the earth is the underpinning of Tesla's proposed "World System." See also magnifying transmitter

earth wire In Tesla's wireless investigations, the wire connected to an earth ground sometimes terminated with a conducting sphere.  The connection to ground may be in common with the master oscillator secondary ground (see CSN, pp. 115, Diagrams 4 & 5, 155, 180), or the ground may be independent.  The circuit may also include a self-inductance coil to lower its period of vibration (see CSN, pp.  161, 162, 174, 177, 184, 191).  It is used in conjunction with a magnifying transformer to facilitate the production of disturbances in the ground and air.  [See CSN, pp.  163, 189, 190 for a modified arrangement.] 

effective radiated power (ERP) The product of the transmitter power in watts and the relative gain of a directional antenna as compared with a standard half-wave dipole.  For example, a transmitter producing 10 watts of power connected to an antenna with a gain factor of 9, has an effective radiated power of 90 watts.  In a given direction, the relative gain of a transmitting antenna with respect to the maximum directivity of a half-wave dipole multiplied by the net power accepted by the antenna from the connected transmitter.

Egg of Columbus A novel demonstration apparatus used to explain the principal of the rotating magnetic field and the induction motor.  It was part of the momentous exhibit at the 1893 Chicago Columbian Exposition at which Tesla and George Westinghouse first introduced the American public to the alternating current electrical power system.

Extremely High Frequency (EHF) The portion of the electromagnetic spectrum between 30 GHz and 300 GHz. 

electric charge Quantity of electricity that flows in electric currents or that accumulates on the surfaces of dissimilar nonmetallic substances that are rubbed together briskly.  It occurs in discrete natural units, equal to the charge of an electron or proton.  It cannot be created or destroyed.  Charge can be positive or negative; one positive charge can combine with one negative charge, and the result is a net charge of zero.  Two objects that have an excess of the same type of charge repel each other, while two objects with an excess of opposite charge attract each other.  The unit of charge is the coulomb, which consists of 6.24 — 1018 natural units of electric charge. (Britannica Concise Encyclopedia, 2004) 

electric dipole Two separated electric charges; a physical structure having the effective centers of positive and negative charges separated.

electric wave A form of electromagnetic wave.  One good example of electromagnetic wave propagation by means of an electric wave is the flow of electrical energy from one end to the other of an RF transmission line, such as coaxial cable.  Strictly speaking, all forms of electromagnetic radiation such as X rays, light, and radio waves exist as an electromagnetic wave, but not all electromagnetic waves are electromagnetic radiation.  Distinct from the Hertz wave

electric field The region around an electric charge in which an electric force is exerted on another charge.  The strength of an electric field E at any point is defined as the electric force F exerted per unit positive electric charge q at that point, or E = F/q.  An electric field has both magnitude and direction and can be represented by lines of force, or field lines, that start on positive charges and terminate on negative charges.  The electric field is stronger where the field lines are close together than where they are farther apart.  The value of the electric field has dimensions of force per unit charge and is measured in units of newtons per coulomb.  (Britannica Concise Encyclopedia, 2004) (See HyperPhysics,) 

electrodynamics The study of phenomena associated with charged bodies in motion and varying electric and magnetic fields; since a moving charge produces a magnetic field, electrodynamics is concerned with effects such as magnetism, electromagnetic radiation, and electromagnetic induction, including such practical applications as the electric generator and the electric motor.  This area of electrodynamics, often known as classical electrodynamics, was first systematically explained by the physicist James Clerk Maxwell. Maxwell's equations, a set of differential equations, describe the phenomena of this area with great generality.  A more recent development is quantum electrodynamics, which was formulated to explain the interaction of electromagnetic radiation with matter, to which the laws of the quantum theory apply.  The physicists P. A. M. Dirac, W. Heisenberg, and W. Pauli were the pioneers in the formulation of quantum electrodynamics.  When the velocities of the charged particles under consideration become comparable with the speed of light, corrections involving the theory of relativity must be made; this branch of the theory is called relativistic electrodynamics.  It is applied to phenomena involved with particle accelerators and with electron tubes that are subject to high voltages and carry heavy currents.  (see charge; electricity) [Source: Fact Monster; The Columbia Electronic Encyclopedia, 6th ed.]

electronic countermeasures (ECM) Actions such as active electronic jamming taken to prevent, degrade or reduce effective use of the electromagnetic spectrum by an enemy, in electronic warfare.

electronic  counter-countermeasures (ECCM) Actions taken to insure friendly effective use of the electromagnetic spectrum despite the enemy's use of electronic warfare.  Also known as electronic protection.

electronic jamming An electronic countermeasure that is the deliberate radiation, re-radiation, or reflection of electromagnetic energy for the purpose of disrupting enemy use of electronic devices, equipment, or systems.  Barrage jamming involves simultaneous electronic jamming over a broad band of frequencies.  Various types of jamming signals include bagpipes, crypto spoofing, FSK spoofing, white noise, modulated white noise, sine wave, random tones, stepped tones, and swept tones.

electronic warfare (EW) Military action involving the use of electromagnetic energy to determine, exploit, reduce or prevent hostile use of the electromagnetic spectrum and action which retains friendly use of the electromagnetic spectrum.  Any military action involving the use of electromagnetic and directed energy to control the electromagnetic spectrum or to attack the enemy.  The three major subdivisions within electronic warfare are electronic attack--the use of electromagnetic or directed energy to attack personnel, facilities, or equipment with the intent of degrading, neutralizing, or destroying enemy combat capability; electronic protection--actions taken to protect personnel, facilities, and equipment from any effects of friendly or enemy employment of electronic warfare that degrade, neutralize, or destroy friendly combat capability; and electronic warfare support--actions tasked by, or under direct control of, an operational commander to search for, intercept, identify, and locate sources of intentional and unintentional radiated electromagnetic energy for the purpose of immediate threat recognition.  See electronic countermeasures, electronic counter-countermeasures and electronic warfare support measures.

electronic warfare support measures (ESM) Actions taken under direct control of a military commander to search for, intercept, identify, and locate sources of radiated electromagnetic energy for the purpose of immediate threat recognition.  A source of information required for immediate decisions involving Electronic Countermeasures, Electronic Counter-Countermeasures, avoidance, targeting, and other tactical employment of forces.

electromagnetism The physics of the electromagnetic field: a field, encompassing all of space, composed of the electric field and the magnetic field. . . . [Source: Wikipedia.]

electromagnetic coupling The transfer of electromagnetic energy from one circuit or system to another circuit or system.  An undesired transfer is termed EMI (electromagnetic interference). 

electromagnetic energy The energy stored in an electromagnetic field.

electromagnetic field . .  .  See also electromagnetic radiation.

electromagnetic induction Induction of an electromotive force in a circuit by varying the magnetic flux linked with the circuit.  The phenomenon was first investigated in 1830-31 by Joseph Henry and Michael Faraday, who discovered that when the magnetic field around an electromagnet was increased or decreased, an electric current could be detected in a separate nearby conductor.  A current can also be induced by constantly moving a permanent magnet in and out of a coil of wire, or by constantly moving a conductor near a stationary permanent magnet.  The induced electromotive force is proportional to the rate of change of the magnetic flux cutting across the circuit. (Britannica Concise Encyclopedia, 2004

electromagnetic interference (EMI) Any induced, radiated, or conducted electrical emission, disturbance, or transient that causes undesirable responses, degradation in performance, or malfunctions of any electrical or electronic equipment, device, or system.  Also synonymously referred to as RFI (Radio Frequency Interference). 

electromagnetic pulse (EMP) The generation and radiation of a very narrow and very high-amplitude pulse of electromagnetic noise.  It is associated with the high level pulse as a result of a nuclear detonation and with intentionally generated narrow, high-amplitude pulse for ECM applications.  In the case of nuclear detonations, EMP consists of a continuous spectrum with most of its energy distributed through the low frequency band of 3 KHz to 1 MHz. 

electromagnetic radiation Electrical energy propagated through free space; a form of electromagnetic wave.  Examples include radio waves, infrared light, visible light, ultraviolet light, X rays, and gamma rays.  Electromagnetic radiation exhibits wave-like properties such as reflection, refraction, diffraction, and interference, but also exhibits particle-like properties in that its energy occurs in discrete packets, or quanta.  Though all types of electromagnetic radiation travel at the same speed, they vary in frequency and wavelength, and interact with matter differently.  A vacuum is the only perfectly transparent medium; all others absorb some frequencies of electromagnetic radiation. (Britannica Concise Encyclopedia, 2004)

electromagnetic wave Electrical energy propagated through a material medium or free space Examples include the propagating electric and magnetic field energy associated with an electric current flowing in a conductor and light travelling through an optical fiber; radio waves, infrared light, visible light, ultraviolet light, X rays, and gamma rays.  Strictly speaking, all forms of electromagnetic radiation such as X rays, light, and radio waves exist as an electromagnetic wave, but not all electromagnetic waves are electromagnetic radiation.  One good example of electromagnetic wave propagation that is not by means of electromagnetic radiation is the flow of electrical energy from one end to the other of an RF transmission line, such as coaxial cable.  See  plasma electromagnetic wave, and electromagnetic radiation see also Hertz wave.

electromagnetic weapon Any device which can produce an electromagnetic field of such intensity that targeted items of electronic equipment experience either a SOFT KILL or a HARD KILL.  [10:2824]

electromagnetically induced transparency (EIT) A technique that makes normally opaque substances transparent to light by applying another source of light, such as a laser beam, that interferes with the opaque substance's absorption of light.  This property was first demonstrated (ca.  2000) by Harvard physicist Lene Hau.  A pulse of light was stopped, stored briefly within a substance, and then released on command.  Source:  Space & Electronic Warfare Lexicon

electro-motive force (EMF) 

electromagnetic spectrum The range of frequencies of electromagnetic radiation from zero to infinity.  Also called frequency spectrum.  The radio frequency portion of the electromagnetic spectrum is presently divided into 11 ranges.


Not yet defined

lower than ULF radio

RADIO SPECTRUM (radio-wave propagation)



3 Hz - ? HZ



3 Hz - 3 kHz



3 - 30 kHz



30 - 300 kHz



300 kHz - 3 MHz



3 - 30 MHz



30 - 300 MHz



300 MHz - 3 GHz



3 - 30 GHz



30 - 300 GHz


300 GHz - 1 THz


Infrared light

.003 - 4 x 1014 Hz

Visible light

4 - 7.5 x 1014 Hz

Near ultraviolet light

7.5 x 1014 - 3 x 1016 Hz

Far ultraviolet light


Soft X rays

3 x 1016 Hz upward

Hard X rays

Gamma rays

Not yet defined

electron A subatomic particle.  (See Wikipedia.)

electron gas See Lorentz gas

electrostatic induction A modification in the distribution of electric charge on one material under the influence of an electric charge on a nearby object.  It occurs whenever any object is placed in an electric field. When a negatively charged object is brought near a neutral object, it induces a positive charge on the near side of the object and a negative charge on the far side.  If the negative side of the original object is momentarily grounded, the negative charge may escape, so that the object becomes positively charged by induction.  (Britannica Concise Encyclop—dia, 2004)  (See GCSE Physics for a demonstration of this principle.  See also Charging by Electrostatic Induction and Induction: What It Means to ESD.)  See dielectric displacement current.

electrostatic machine A generator which produces an electric charge by friction or electrostatic induction.  One of the first of these machines was built by Cavallo around 1777.  Other names associated with these devices are Wimshurst, Holtz, Toepler, Wommelsdorf, and Van de Graaff (ca.  1933).

electrostatic unit (esu) A unit of electric charge that exerts a force of 1 dyne on another unit of charge at a distance of 1 centimeter in a vacuum (cgs).

electrostatic wave or plasma electrostatic wave One of three categories of plasma waves: electromagnetic, electrostatic, and hydrodynamic (magnetohydrodynamic).  Wave motions, i.e.  plasma oscillations, are inherent to plasmas due to the ion/electron species, electric/magnetic forces, pressure gradients, and 'gas-like' properties that lead to shock waves.  Electrostatic waves are longitudinal oscillations appearing in plasma due to a local perturbation of electric neutrality.  For a cold, unmagnetized plasma, the frequency of electrostatic waves is at the "plasma frequency" [Source: Plasma Dictionary]


elevated capacity See terminal capacity

energy density (electromagnetic field) The electromagnetic energy contained in an infinitesimal volume divided by that volume.

ether An hypothesized all pervasive elastic medium by which Tesla believed wireless energy transmission is achieved, by the alternating compression and rarefaction of same.  He described the ether as "a ponderous medium of coarse particles, or bodily carriers of force" [The Transmission of Electrical Energy Without Wires as a Means for Furthering Peace], concluding it was "a medium . . . composed of particles immeasurably smaller than those of air . . . [a] gas . . . so light that a volume equal to that of the earth would weigh only about one-twentieth of a pound." He further stated, "The velocity of any sound wave depends on a certain ratio between elasticity and density, and for this ether or universal gas the ratio is 800,000,000,000 times greater than for air. This means that the velocity of the sound waves propagated through the ether is about 300,000 times greater than that of the sound waves in air, which travel at approximately 1,085 feet a second. Consequently the speed in ether is 900,000 x 1,085 feet, or 186,000 miles, and that is the speed of light." [Nikola Tesla Tells of New Radio Theories]  William Crookes described the ether as a, "highly attenuated medium" and "a diviner air" to differentiate it from "the gross [gaseous earth] atmosphere."
     Theorizing about the existence of an ether is classified as protoscience.  One of the present theories requires that ether be described in terms of energy rather than mass.  It implies that if the ether could be seen, it would appear as a lattice-like array of electric charges, all identical, immersed in a uniform background continuum of opposite charge polarity.  Overall, it would be electrically neutral, having properties akin to those of a fluid crystal.  When matter was present, the electrical action of its charge components would cause the lattice to form a frame of reference locked to the matter frame and it would be possible for this to move bodily with that matter.  This would form boundaries between lattice regions in relative motion.  The fluid crystal property would then assert itself as the lattice charges at the forward boundaries dissolved into the fluid background only to reappear at the trailing boundary.  (This is a version of the ether that was not considered by the aether theorists of the 19th century.)  Its structure determines the most important dimensionless constant in physics, namely the one which connects the speed of light with the electron unit of charge and the quantum of action we associate with radiation.  The ether has a kind of rhythmic jitter motion, which is shared by all matter.  The ether lattice charges appear to be at rest, given that relative motion is all we can sense, but that is not dependent upon the doctrines of Einstein's Theory of Relativity.  It is a feature of the ether, because the charge lattice defines the local electromagnetic reference frame and it adapts to the uniform motion of the system of matter shared by the observer. [Source: Energy Science, AN INSIGHT INTO THE AETHER, Harold Aspden] See also quantum vacuum.  See also aether.

extremely low frequency (ELF) The portion of the electromagnetic spectrum between 3 Hz and 3 kHz.  [30-300 Hz]

Faraday rotation The orientation of the electric field vector of an electromagnetic wave propagating parallel to a magnetic field embedded in a plasma rotates as the wave propagates.  This rotation is called Faraday rotation and measurements of it can be used to deduce the strength of the magnetic field.  [Source: Plasma Dictionary]

feedline or feeder alternate terms for a transmission line.

field strength The magnitude of a magnetic or electric field at any point, usually expressed in terms of ampere turns per meter or volts per meter.  Sometimes called field intensity and is expressed in volts/meter or dBv/meter.

fluorescent lamp A gas-filled lamp in which light is produced by ultraviolet radiation causing the fluorescence of phosphors lining the lamp's glass tube or enclosure.

foot candle A measure of light intensity on a surface being illuminated.  Defined as one lumin of light per one square foot of surface area. 

force-free currents Currents which run parallel to the total magnetic field and therefore experience no Lorentz (J cross B) force. [Source: Plasma Dictionary]

frequency The rate of alteration in an electric current or electromagnetic wave, expressed in cycles per second or Hertz (Hz).  The number of complete cycles of a periodic waveform per unit time. 

frequency hopping A spread spectrum communications technique in which a wireless transmitter and receiver are programmed to hop from frequency to frequency simultaneously.

frequency modulation (FM) A form of modulation in which the frequency of the modulated carrier wave is varied in proportion to the amplitude of the modulating wave.  In this case the phase of the carrier varies with the integral of the modulating wave.  See also modulation.

frequency multiplication .  .  .

fully ionized plasma A plasma in which all the atoms or molecules have been ionized.  Compare to weakly ionized plasma. [Source: Plasma Dictionary] (See also plasma

gauss A unit of magnetic flux density equal to 10 -4 weber per meter square.

generator A rotary electrical machine for producing direct current.  May also refer to an electrical alternator.

glow discharge Low-density, low-temperature plasma discharge (such as in a fluorescent light) which, well, glows.  Sputtering in glow discharges is useful in plasma processing of materials.  The voltage applied to the plasma must be greater than the ionization potential of the gas used; most of the plasma voltage drop is near the cathode, where the majority of ionization occurs.  Discharge is sustained by secondary electrons emitted when ions or recombination radiation impact on the cathode; electrons are accelerated away from the cathode and ionize neutral gas in the discharge.  [Source: Plasma Dictionary]

ground The point within the earth's surface where effective ground conductivity exists.  The depth of this point varies with the frequency, the condition of the soil and the geographical region

ground plane A system of electrical conductors placed below an antenna to serve as an earth ground (see also counterpoise).

ground wave The portion of the radiated space wave that propagates close to the surface of the Earth.  The ground wave has direct-wave and ground-reflected components and under certain conditions a tropospheric ducting component.  There is also an induced ground-hugging surface-wave component.  The direct component of the ground wave is limited only by the distance to the horizon from the transmitter plus a small distance added by atmospheric diffraction around the curvature of the earth.  The ground-reflected component is the portion of the radiated wave that reaches the receiving antenna after being reflected from the Earth's surface.  The surface-wave component is the result of electrical currents induced in the ground by refraction of a portion of the reflected-wave component at the Earth-atmosphere interface.  See Hertz antenna and Marconi antenna; see also sky-wave.

Ground Wave Emergency Network (GWEN) An LF governmental wireless telecommunications system designed to  provide survivable connectivity to designated bomber and tanker bases by surviving massive broadband destructive interference produced by nuclear explosions, and recovering quickly from the changes in radiowave propagation caused by the ionization of atoms in the upper atmosphere.  GWEN operations were decommissioned in 2000.

guiding center Particles placed in a magnetic field will gyrate in circles around the magnetic field lines, and drift in various directions.  The guiding center represents the instantaneous center of the circular motion.  The idea is that you can think of the guiding center as drifting, and the particle as orbiting the guiding center.  [Source: Plasma Dictionary]

Gyrotron A device for producing microwave energy that utilizes a strong axial magnetic field in a cavity resonator to produce azimuthal bunching of an electron beam.  [Source: Plasma Dictionary]

helical antenna An antenna constructed in the form of a helix.  When the circumference is one wavelength, circularly-polarized electromagnetic waves are generated with maximum radiation occurring along the helix axis.  In order to radiate efficiently the helix must have sufficient pitch so the wave's E-field can rotate through 360— in the time it takes for the wave disturbance to travel one wavelength along the axis.  When the helix circumference is much smaller than one wavelength, the antenna radiates at right angles to the axis of the helix (see slow-wave helical resonator).

H-field see magnetic field

H-field probe A small Faraday screened loop antenna used for the detection of low impedance near field current sources.

hertz (Hz) The unit of frequency equal to one cycle per second.

Hertz antenna a 1/2-wave electric dipole antenna in free space, approaches an ideal source of electromagnetic radiation emitted in the form of space waves.  These space waves can reach the receiver either by ground-wave propagation or by reflection from the ionosphere, known as sky-wave propagation.  See also Marconi antenna and Tesla antenna.

Hertzian radiation See Hertz wave 

Hertz wave Also known as electromagnetic radiation, named after Heinrich Rudolf Hertz who in 1888 first demonstrated that a resonating electric circuit can transfer electromagnetic energy to another resonate electric at a distance, without wires.  It is characterized by a variation of the electric and magnetic fields in the far-field region associated with a radiating antenna.  Along with the energy lost or radiated from a radio antenna, a certain fraction of the energy is also returned during each radio-frequency cycle, meaning the radiation fields associated with a transmitter's antenna represent both energy storage and far-field radiation components.  See also antenna regions.

high-field emission Also known as Fowler/Nordheim emission.  The discharge of electrons from the surface of a material subjected to a strong electric field.  In the absence of a strong electric field, an electron must acquire a certain minimum energy, called the work function, to escape through the surface of a given material, which acts as a barrier to electron passage.  The application of a high voltage between a fine point cathode and a contra surface can, by a tunneling effect, give sufficient energy to an electron so that it escapes from the surface.  The electric field around a point is greatly enhanced relative to the apparent average electric field between the electrodes.  High current densities can be attained but the actual current will be small due to the small surface of the emitter.  Larger currents can be obtained by multiplying the emitter sites.  Needles or razor blades can be used as emitter arrays, and arrays etched in silicon have shown some success in electron tubes.  A disadvantage of this type of source is that an excessive current density can destroy the points either by erosion or self heating.  The unique properties of diamond, including low electron affinity, wide band-gap, chemical stability, resistance to particle bombardment, hardness and good thermal conductivity, could prove beneficial for emitter arrays.  Very high field emission current with diamond might be achieved at room temperature by a well-patterned diamond microtip.  (see Encyclop—dia Britannica, Linac Basics and Diamond Microtip Vacuum Field Emitter Structures.)  High-field emission may take place at the elevated terminal capacity of a full scale magnifying transmitter.

High Frequency (HF) The portion of the electromagnetic spectrum between 3000 kHz and 30,000 kHz.

high frequency inverter ballast 

hybrid resonance A resonance in a magnetized plasma which involves aspects of both bunching of lighter species parallel to the magnetic field, characterized by the plasma frequency; and perpendicular particle motions (heavier species) characterized by the cyclotron frequency.  [Source: Plasma Dictionary]

IGBT insulated gate bipolar transistor

impedance The ohmic value of an antenna feedpoint, matching section or a transmission line.  An impedance may contain a reactance as well as resistance component. 

induction motor An alternating current electric motor in which the wear-prone commutator and brushes commonly found in direct current motors have been eliminated.  In industrial applications these motors are powered by three phase alternating current.  Arrangements have been developed that allow their use with single phase current as well.  In operation, the successive electrical alternations and a rotating motion of the stator's magnetic field, caused by the separate phases of the alternating current, combine to induced a voltage in the rotor windings.  The resulting current flowing in the rotor windings produces additional magnetic fields which interact with the original rotating magnetic field resulting in rotary motion.  It might be said that the induction motor is a rotating transformer.  The demonstration of a 1/5 horsepower two-phase induction motor at Columbia University on May 16, 1888, before the American Institute of Electrical Engineers, helped to usher in a new era of cheap and abundant electrical energy.  See also rotating magnetic field

inductively coupled discharge A plasma created by applying an oscillating, radiofrequency potential to an inductive coil.  The oscillating current in the coil creates an oscillating magnetic field, which in turn induces an oscillating electric field.  Power is coupled to the plasma through the acceleration of electrons by the oscillating electric field.  [Source: Plasma Dictionary]

inductor A length of wire or other conductor generally wound around a cylindrical tube or framework to form a coil.

insulator A material having a high resistance to the passage of an electrical current.  See also dielectric

internal capacitance Also known as distributed capacitance and self capacitance.  The capacitance that exists between the adjacent windings of an inductor because of their proximity to each other.  An inductor may act as though it includes a parallel capacitor, because of its closely spaced windings.  When a potential difference exists across the coil, wires lying adjacent to each other at different potentials are affected by each other's electric field.  They act like the plates of a capacitor, and store charge.  Any change in the voltage across the coil requires extra current to charge and discharge these small 'capacitors.'  When the voltage changes only slowly, as in low-frequency circuits, the extra current is usually negligible, but when rapid voltage changes occur the extra current is larger and can be significant.  See also parasitic capacitance

international coulomb A unit of electric charge equal to 0.999835 coulomb. Standard coulomb prior to 1950.


ion acoustic wave A longitudinal compression wave in the ion density of a plasma.  For more information see (e.g.) Stix, Thomas Howard.  "Waves in Plasmas" American Institute of Physics, New York, 1992. [Source: Plasma Dictionary]

ionosphere A region of space surrounding a planet and its neutral atmosphere, containing both neutral and ionized gases.  The Earth's ionosphere extends from 90 km to a few thousand kilometers, where it merges with the plasmasphere and the magnetosphere.  [Source: Plasma Dictionary]

IP Internet Protocol

ITU International Telecommunication Union

isochronous Time-dependent.  Pronounced eye-sock-ra-nuss, it refers to processes where data must be delivered within certain time constraints.  For example, multimedia streams require an isochronous transport mechanism to ensure that data is delivered as fast as it is displayed and to ensure that the audio is synchronized with the video. 
Isochronous can be contrasted with asynchronous, which refers to processes in which data streams can be broken by random intervals, and synchronous processes, in which data streams can be delivered only at specific intervals.  Isochronous service is not as rigid as synchronous service, but not as lenient as asynchronous service. 
     Certain types of networks, such as ATM, are said to be isochronous because they can guarantee a specified throughput.  Likewise, new bus architectures, such as IEEE 1394, support isochronous delivery.  []
     Unlike asynchronous and synchronous communication, which both involve elaborate error checking mechanisms, the driving force behind isochronous communication is a fast, steady, uninterrupted data stream.  Isochronous clocking information is derived from or included in the data stream, and the delay factor is dependent on a channel's characteristics and can be logically determined.  Communication can be disrupted if the transmitter does not maintain a constant transfer rate, or if the receiver has an insufficient buffer to store data at the rate it is arriving and then hold it until it can be processed by software.  To maintain data transfer speed, error checking is often omitted.  Though software can be written to track errors, there is no hardware mechanism by which to request retransmission of corrupted data.
     Isochronous communication is best suited for applications where a steady data stream is more important than accuracy.  A good example is video conferencing where infrequent small —blips" in the data stream are tolerable, however, long pauses between a transmission and a response are not.
     To ensure that isochronous transfers are not bogged down by other devices, the USB specification sets aside bandwidth for them.  []
     /i:-sok'rn-*s/ A form of data transmission that guarantees to provide a certain minimum data rate, as required for time-dependent data such as video or audio.
     Isochronous transmission transmits asynchronous data over a synchronous data link so that individual characters are only separated by a whole number of bit-length intervals.  This is in contrast to asynchronous transmission, in which the characters may be separated by arbitrary intervals, and with synchronous transmission.
     Asynchronous Transfer Mode and High Performance Serial Bus can provide isochronous service.
     Compare: plesiochronous.  [ [ANIXTER, LAN Magazine 7.93]]

isotropic antenna A hypothetical loss-less antenna which radiates or receives energy equally in all directions.  Used as a zero dB gain reference in directivity calculation (gain).  The sun is often given as an example of an isotropic radiator.  The isotropic antenna provides a convenient reference for expressing the directive properties of actual antennas. 

isotropic capacity In general, any conductive body removed by ten times its major axis length from the presence of other bodies may be considered electrostatically isotropic.  Envision two concentric metal spheres forming a capacitor with the intervening air or vacuum being the dielectric medium.  Charged it from a source of electrical energy.  Imagine that electric field lines now exist between the two spheres.  Due to the regularity of their surfaces and one of the laws of electrostatics, the lines of electric charge distribute themselves uniformly over the entire surfaces of both spheres.  The energy within the capacitor is fixed.  The geometry dictates that for a given number of field lines the number per unit area on the inner sphere will be higher than on the outer sphere.  Increase the diameter of the outer sphere.  The number of lines per unit of area on the inner sphere remains the same but the number of lines per unit of area on the outer sphere decreases as it recedes to infinity.  From this it can be seen that charge can be separated in space and one sign of it can be effectively placed on an isolated sphere.  This ideal model ignores the rest of the material universe.  The charges' opposite signs are assumed to be at infinity.  In reality, the complementary charges are distributed over the many other material surfaces which comprise the physical environment. The sphere appears to be a single plate capacitor [that can be charged and discharged with relation to other matter].  The separated charge is never on the small sphere, but in the space around it.  One sign of the total charge is concentrated around the interfacial boundary of the sphere and the dielectric medium in contact with it. 

 joule The joule (symbol J, also called newton meter, or coulomb volt) is the SI unit of energy and work.  The unit is pronounced to rhyme with "tool", and is named in honor of the physicist James Prescott Joule 
(1818-1889).  [Source:] 

Kinetic Theory A theoretical approach which attempts to explain the behavior of physical systems using the assumptions that the systems are composed of large numbers of atoms/molecules/particles in vigorous motion, that energy and momentum are conserved in collisions of these particles, and that statistical methods can be applied to deduce the behavior of such systems.  Kinetic theory has been applied to plasmas with considerable success, but is often computationally intensive.  [Source: Plasma Dictionary]

Kirchoff's 1st Law The term direct current (DC) refers to current that flows with constant magnitude and direction.  One simple DC circuit consists of a voltage source (battery or voltaic cell) connected to a resistor.

Kirchoff's 1st Law states that the current flowing into a junction in a circuit (or node) must equal the current flowing out of the junction.  This law is a direct consequence of the conservation of charge.  Since no charge can be lost in the junction, any charge that flows in must ultimately flow out.  Kirchoff's 1st Law can be remembered as the rule that uses nodes to study the flow of current around a circuit.   [Source:] 

Kirchoff's 2nd Law This law states that for any closed loop path around a circuit the sum of the voltage gains and voltage drops equals zero.  In the circuit shown, there is a voltage gain for each electron traveling through the voltage source (symbolized by ) and a voltage drop across the resistor ( iR).  Applying Kirchoff's law:

Note that this result has the same form as Ohm's law:

Kirchoff's 2nd Law is based on the principle of conservation of energy.  No energy can be lost from or gained by the circuit, so the net voltage change must be 0.  Kirchoff's 2nd Law can be remembered as the rule that uses loops to study the flow of current around a circuit.  [Source:] 

Larmor radius The radius of the path of a charged particle moving in a magnetic field (and transverse to the field lines).  Also known as gyroradius and cyclotron radius.  The Larmor radius can be readily determined by balancing the centripetal Lorentz (F = q/c v-cross-B) force with the equation for circular motion (F = mv^2/r) to get r = (c m / q) v_perp/B. See also magnetohydrodynamics. [Source: Plasma Dictionary]

Lambda () The Greek symbol used to represent a wavelength with reference to electrical dimensions in radio-frequency work

Low Frequency (LF) The portion of the electromagnetic spectrum between 30 kHz and 300 kHz. 

LC circuit A radio frequency electrical circuit composed of an inductor and a capacitor.  An LC circuit exhibits resonance at a specific frequency which is determined by the value of the inductor and the capacitor. 

Leyden jar An early form of electrical condenser or capacitor consisting of a glass container lined inside and out with metal foil.

longitudinal waves Waves where the variation of the field is partially or totally in the direction of propagation (parallel to wavennumber, k [a vector]).  Examples include sound waves and Langmuir waves.  Contrasted with transverse waves, where the variation is perpendicular to the direction of propagation, such as light waves.  - John Cobb [Source: Plasma Dictionary]

Lorentz Force Law (J cross B) (See also force-free currents) (See HyperPhysics and Science Joy Wagon.)

Lorentz gas A Plasma model in which the electrons are assumed not to interact with each other, but only with ions (Z -> infinity) and where the ions are assumed to remain at rest (ion mass approximated as infinity). Also known as "electron gas."  [Source: Plasma Dictionary]

 mach number The ratio of the velocity of a body to the speed of sound in the medium that is being considered.  In the atmosphere, the speed of sound varies with temperature and atmospheric pressure, hence, so does mach number.

Marconi antenna  A modified 1/2-wave dipole Hertz antenna.  It is adapted to the real-world conditions encountered in the construction of low and medium frequency transmitters.  These adaptations are imposed by the wavelength involved and the resulting physical dimensions required of the antenna.  The dipole antenna is modified in that its lower half, 1/4 wavelength long, exists only as a mirror image of its upper counterpart.  The resulting 1/4-wave vertical 'monopole' antenna takes advantage of the fact that at low frequencies the ground acts as a mirror for the radiated energy.  The ground reflects a large amount of the energy that is radiated downward from the antenna mounted over it.  In the physical construction of the ground connection is important to have as high a conductivity as possible.  The object is to provide the best possible reflecting surface for the downward radiated energy from the antenna.  Typically, the ground consists of a number of bare conductors arranged radially and connected, 1/2 wavelength long, buried a short distance [6-8 inches] beneath the earth's surface.  In practice these conductors may act as part of the reflecting surface as well as making the connection to ground itself.  An alternative type of ground is the counterpoise.  It is a wire structure erected a short distance above the ground, and insulated from the ground.  Prevailing antenna theory says the counterpoise operates by virtue of its capacitance to the ground.  Not unlike the Hertz antenna, the Marconi antenna is intended as a source electromagnetic radiation in the form of space waves.  See also  Hertz antenna and Tesla antenna.

magnetic field (H)  Any space or region in which the magnetic force created by a permanent magnet or by a current-carrying conductor or coil can be detected.

magnetic pressure The pressure which a magnetic field is capable of exerting on a plasma; equal to the magnetic energy density; proportional to B^2.  (The proportionality constant is 1/(2*mu_0) in SI units, 1/8pi in CGS units).  [Source: Plasma Dictionary]

magnetic reconnection When a plasma has some resistivity, then the frozen-in flow requirement is relaxed (see frozen-in flow).  In that case, the magnetic field can move through the plasma fluid on the resistive (magnetic diffusion) time scale.  (This is typically slow compared to MHD timescales.) This allows field lines to reconnect with each other to change their topology in response to magnetic and other forces in the plasma.  (See also Helicity, which is not conserved when reconnection is significant.) During reconnection, magnetic flux annihilates and transforms into plasma kinetic energy.  For example, the predominant theory for solar flares is based on the transfer of energy from magnetic fields to plasma particles which can occur in reconnection.  Reconnection is also studied in the laboratory.  In many practical cases reconnection occurs even when the plasma is "collision less," i.e.  its collisional resistivity is much too small to explain the short reconnection time scales that are observed.  [Source: Plasma Dictionary]

magnetron Class of vacuum devices with a closed ExB path for electron circulation.  The term is used for both microwave sources and for sputtering discharges.  The latter are widely used for physical vapor deposition (PVD) of thin films; they use magnets located behind an electrode to confine electrons, thereby allowing a plasma discharge to be sustained by electron-impact ionization at a reduced gas pressure, and enhancing the sputtering rate due to ion bombardment of the electrode.  [Source: Plasma Dictionary]

magnetohydrodynamic instability (MHD instability) The class of unstable (growing, not damped) waves and other modes of oscillation, which are described by MHD theory.  [Source: Plasma Dictionary]

magnetohydrodynamic waves Material (fluid) waves in an electrically conducting fluid in the presence of a magnetic field.  They are described by magnetohydrodynamics (MHD), a physical model of electrically conducting fluids interacting with magnetic and electric fields.  MHD theory is relevant at relatively low frequencies and for distance scales larger than the Larmor radius.  Also known as hydromagnetics.  [Source: Plasma Dictionary]

magnetohydrodynamics (MHD) Also known as hydromagnetics or magnetofluiddynamics, this is the academic discipline which studies the dynamics of electrically-conducting fluids and their interactions with magnetic fields.  Examples of such fluids include plasmas and liquid metals.
     The set of equations which describe MHD are a combination of the Navier-Stokes equations of fluid dynamics and Maxwell's equations of electromagnetism.  These differential equations have to be solved for simultaneously. This is too complex or impossible to do symbolically in all but the most trivial cases.  For real-world problems, numeric solutions are found using supercomputers. [Source: Wikipedia.] 
     MHD theory is relevant at relatively low frequencies and for distance scales larger than the Larmor radius.   [Source: Plasma Dictionary

magnifying transmitter An advanced type of Tesla electrical oscillator or Tesla coil specifically intended for wireless transmission.  In addition to the primary and secondary inductors characteristic of the classic Tesla coil, Tesla added a third inductor known as the "extra coil."  In practice, this helical resonator is physically separated from the other two coils which comprise the master oscillator section, this in order to minimize inductive coupling between the two systems.  Power from the two-coil master oscillator section is fed to the lower end of the extra coil resonator through a heavy electrical conductor.  See Tesla's U.S. patent APPARATUS FOR TRANSMITTING ELECTRICAL ENERGY See also Tesla coil and World System.

Maxwell's equations The set of four equations, attributed to James Clerk Maxwell, that describe the behavior of both the electric and magnetic fields, as well as their interactions with matter.  They express, respectively, how electric charges produce electric fields (Gauss's law), the experimental absence of magnetic charges and how currents produce magnetic fields (Amp—re's law), and how changing magnetic fields produce electric fields (Faraday's law of induction).  In 1865 they were used to predict that waves of oscillating electric and magnetic fields travel through empty space at a speed that could be determined from simple electrical experiments.  Using the data available at the time, Maxwell obtained a velocity of 310,740,000 m/s, approximately the speed of light.  [Source: Wikipedia.]

medium frequency (MF) The portion of the electromagnetic spectrum between 300 kHz and 30,000 kHz.

megahertz (MHz) One million (1,000,000) hertz.

microvolt per meter (:V/m) A commonly used unit of field strength at a given point.  The field strength is measured by locating a standard receiving antenna at that point, and the "microvolts per meter" value is then the ratio of the antenna voltage in microvolts to the effective antenna length in meters.  Usually used below 100 MHz.  Above 100 MHz, power density terminology is normally used. 

microwaves Electromagnetic waves of sufficiently short wavelength that practical use can be made of waveguide and associated cavity techniques in their transmission and reception.  Note: the term is taken to signify waves having a frequency range of 300 MHz-300 GHz.

mixer A device which utilizes its non-linear characteristics to provide frequency conversions from one frequency to another.  This may be from a relatively high frequency to an intermediate frequency (IF).  In this case it is known as a down-mixer.  Or it may be from a lower frequency to a higher frequency, the carrier frequency, for example.  In this case it is known as an upmixer. 

mode A manner of doing, method, way; the manner of a thing's existence.  In telecommunications, transmission mode, modulation mode, propagation mode, etc. 

modulation The process of varying the amplitude, frequency, or phase of an RF carrier wave.  The process whereby some characteristic of one wave is varied in accordance with some characteristic of another wave.  The basic types of modulation are angle modulation, including the special cases of phase modulation and frequency modulation, and amplitude modulation.

Navier-Stokes equations In fluid dynamics, the equations named after Claude-Louis Navier and George Gabriel Stokes. They are a set of nonlinear partial differential equations that describe the flow of fluids such as liquids and gases. For example: they model weather or the movement of air in the atmosphere, ocean currents, water flow in a pipe, as well as many other fluid flow phenomena.

near-field region A volume of space generally in proximity to an antenna or other radiating structure, in which the electric and magnetic fields do not have a substantially plane-wave character, but vary considerably from point to point.  The near-field region is further subdivided into the reactive near-field region, which is closest to the radiating structure and that contains most or nearly all of the stored energy, and the radiating near-field region where the radiation field predominates over the reactive field, but lacks substantial plane-wave character and is complicated in structure. 

non-ionizing radiation (NIR) Non-ionizing electromagnetic radiation incorporates all radiations and fields of the electromagnetic spectrum that do not normally have enough energy to produce ionization in matter.  NIRs have an energy per photon less than about 12eV, wavelengths longer than 100 nm, and frequencies lower than 300 THz. 

node A point in a standing or stationary wave at which the amplitude is a minimum.

Norton surface wave The ground-wave component of a space wave resulting from refraction of a portion of the reflected-wave component at the Earth-atmosphere interface and induction of electrical currents in the ground.  Upon reflection from the Earth's surface the reflected wave undergoes a 180deg phase reversal.  When both transmitting and receiving antennas are on, or close to, the ground, and the distance between them becomes great, the direct and reflected components tend to cancel out, and the resulting field intensity is principally that of the surface wave.  Because part of its energy is absorbed by the ground, the electrical intensity of the surface wave is attenuated at a much greater rate than inversely as the distance.  It is the conductivity of the underlying terrain that determines the attenuation of the surface-wave field intensity as a function of distance.  The ground currents of a vertically polarized surface wave do not short-circuit a given electric field but rather serve to restore part of the used energy to the following field.  The better the conducting surface layer, the more energy returned and the less energy absorbed.

null A condition during which an electrical property is at minimum. 

Ohm's law A statement of the relationship of current, voltage, and resistance in dc electrical circuits.  The current in a circuit is directly proportional to the voltage and inversely proportional to the resistance.  It may be expressed by any one of three equations: I = E/R , R = E/I , E = IR, where I = current, E = voltage, and R = resistance.

parametric oscillation This occurs when one of the parameters of the system is varied.  A child can "pump" a swing by standing and raising and lowering her center of mass periodically, changing the length of the pendulum. The child pumps at twice the pendulum frequency, generating a sub harmonic.  A very simple demonstration of parametric oscillation is the coupling of the pendulum mode to a mass on a spring. When the spring frequency is approximately twice the swinging frequency (pendulum mode), the spring mode parametrically drives the pendulum mode, but the pendulum motion causes the tension in the spring to vary at twice the pendulum frequency, and therefore resonantly drives the spring mode.  The transfer of energy between these two modes is impressive. [Source: UCLA Physics Demoweb]

particle beam, charged A projected stream of charged particles.  Tesla's purported teleforce device is said to project macroscopic particles of a material such as mercury or tungsten.  The advantage of a particle beam weapon is that target penetration is so high that it is difficult to shield against it. 

particle beam, neutral A projected stream of neutral particles such as deuterium or heavy hydrogen at very high particle energies and low currents.  The atoms are accelerated through electric fields as negative ions with an extra electron attached; then the electron is stripped off in passage through a gas cell, leaving a beam of neutral atoms.  Neutral particle beams must have very long dwell times on a target to produce lethal depositions of energy. 

peak envelope power (PEP) The average power supplied to the antenna transmission line by a transmitter during one radio frequency cycle at the crest of the modulation envelope taken under normal operating conditions.

phase 1. Of a periodic, varying phenomenon, e.g., an electrical signal or electromagnetic wave, any distinguishable instantaneous state of the phenomenon, referred to a fixed reference or another periodic varying phenomenon.  Note 1: Phase, i.e., phase time (frequently abbreviated simply to "phase" in colloquial usage), can be specified or expressed by time of occurrence relative to a specified reference.  Note 2: The phase of a periodic phenomenon can also be expressed or specified by angular measure, with one period usually encompassing 360— (2 radians).  Note 3: Phase may be represented (a) in polar coordinates by M , where M is the magnitude and is the phase angle, and (b) in Cartesian coordinates, i.e. , an Argand diagram, as (a + jb ), where a is a real component and b is an imaginary component such that tan = (b /a ), where is the phase angle, and the magnitude, M , is (a 2 + b 2)  2.  A distinguishable state of a phenomenon.  3.  That period of time during which a specified function occurs in a sequential list of functions.  [source: 

phase lock loop A phase-locked loop (PLL) is an electronic circuit with a voltage- or current-driven oscillator that is constantly adjusted to match in phase (and thus lock on) the frequency of an input signal.  In addition to stabilizing a particular communications channel (keeping it set to a particular frequency), a PLL can be used to generate a signal, modulate or demodulate a signal, reconstitute a signal with less noise, or multiply or divide a frequency.  PLLs are frequently used in wireless communication, particularly where signals are carried using frequency modulation (FM) or phase modulation (PM).  PLLs can also be used in amplitude modulation (AM). PLLs are more commonly used for digital data transmission, but can also be designed for analog information.  Phase-locked loop devices are more commonly manufactured as integrated circuits (ICs) although discrete circuits are used for microwave. 
     A PLL consists of a voltage-controlled oscillator (VCO) that is tuned using a special semiconductor diode called a varactor. The VCO is initially tuned to a frequency close to the desired receiving or transmitting frequency.  A circuit called a phase comparator causes the VCO to seek and lock onto the desired frequency, based on the output of a crystal-controlled reference oscillator.  This works by means of a feedback scheme.  If the VCO frequency departs from the selected crystal reference frequency, the phase comparator produces an error voltage that is applied to the varactor, bringing the VCO back to the reference frequency.  The PLL, VCO, reference oscillator, and phase comparator together comprise a frequency synthesizer.  Wireless equipment that uses this type of frequency control is said to be frequency-synthesized. 
     Since a PLL requires a certain amount of time to lock on the frequency of an incoming signal, the intelligence on the signal (voice, video, or data) can be obtained directly from the waveform of the measured error voltage, which will reflect exactly the modulated information on the signal.,,sid7_gci783790,00.html 

phase modulation The phase of the modulated carrier is varied in proportion to the amplitude of the modulating wave.  See also modulation.

phased array radar Radar using many antenna elements which are combined in a controlled phase relationship.  The direction of the beam can be changed as rapidly as the phase relationships (usually less than 20 microseconds).  Thus, the antenna typically remains stationary while the beam is electronically scanned.  The use of many antenna elements allows for very rapid and high directivity of the beam(s) with a large peak and/or average power.  There is also a potential for greater reliability over a conventional radar since the array will fail gracefully, one element at a time.

photon From Greek φοτος, meaning light.  A quantum of excitation of the quantised electromagnetic field.  One of the elementary particles studied by quantum electrodynamics (QED), which is the oldest part of the Standard Model of particle physics.  In layman's terms, photons are the building blocks of electromagnetic radiation: that is, a photon is a "particle" of light, although, according to quantum mechanics, all particles, including the photon, also have some of the properties of a wave. [Source: Wikipedia] (See also Grokking the Photon)

plasma, thermal and nonthermal Known as the "Fourth State of Matter", a plasma is a substance in which many of the atoms or molecules are effectively ionized, allowing charges to flow freely.  Since some 99% of the known universe is in the plasma state and has been since the Big Bang, plasmas might be considered the First State of Matter.  Plasmas have unique physics compared to solids, liquids, and gases; although plasmas are often treated as extremely hot gases, this is often incorrect.  Examples of plasmas include the sun, fluorescent light bulbs and other gas-discharge tubes, very hot flames, much of interplanetary, interstellar, and intergalactic space, the earth's ionosphere, parts of the atmosphere around lightning discharges, laser-produced plasmas and plasmas produced for magnetic confinement fusion.  Types of plasmas include - Astrophysical, Collisionless, Cylindrical, Electrostatically Neutral, Inhomogeneous, Intergalactic, Interstellar, Magnetized, Nonneutral, Nonthermal, Partially Ionized, Relativistic, Solid State, Strongly Coupled, Thermal, Unmagnetized, Vlasov and more.  [Source: Plasma Dictionary]
     A plasma can be described as a gas to which a specific amount of energy has been added to separate the gas component molecules into a collection of ions, electrons, charge-neutral gas molecules, and other species in varying degrees of excitation.  Depending on the amount of energy added, the resulting plasma can be characterized as thermal or nonthermal.  In a thermal plasma, enough energy is introduced so the plasma constituents are in thermal equilibrium—the ions and electrons are, on average, at the same temperature.  An electrical arc is one example of a thermal plasma, a familiar manifestation of which is a lightning bolt bridging the gap between a storm cloud and the earth.  The temperature of thermal plasma components is about 1-2 electron-volts (1 eV is associated with 11,600 K).  A nonthermal plasma is one in which the mean electron energy, or temperature, is considerably higher than that of the bulk-gas molecules.  Because energy is added to the electrons instead of the ions and background gas molecules, the electrons can attain energies of from 1-10 eV, while the background gas remains at ambient temperature.  This nonthermal condition can be created at both atmospheric and subatmospheric pressures.  The electrons are preferentially excited in a nonthermal plasma, leaving the more massive ions with lower energy.  See cold plasma model. [Source:]

plasma, weakly ionized A plasma in which only a small fraction of the atoms are ionized, as opposed to a highly ionized plasma, in which nearly all atoms are ionized, or a fully ionized plasma, in which all atoms are stripped of all electrons nearly all the time. [Source: Plasma Dictionary]

plasma discharge Low-density, low-temperature plasma discharge (such as in a fluorescent light) which, well, glows.  Sputtering in glow discharges is useful in plasma processing of materials.  The voltage applied to the plasma must be greater than the ionization potential of the gas used; most of the plasma voltage drop is near the cathode, where the majority of ionization occurs.  Discharge is sustained by secondary electrons emitted when ions or recombination radiation impact on the cathode; electrons are accelerated away from the cathode and ionize neutral gas in the discharge.  [Source: Plasma Dictionary]

plasma electromagnetic wave One of three categories of plasma waves: electromagnetic, electrostatic, and hydrodynamic (magnetohydrodynamic).  Wave motions, i.e.  plasma oscillations, are inherent to plasmas due to the ion/electron species, electric/magnetic forces, pressure gradients, and 'gas-like' properties that can lead to shock waves.  [Source: Plasma Dictionary]

plasma electrostatic wave See electrostatic wave

plasma frequency The natural collective oscillation frequency of a charge species (electrons, ions, etc.) in a plasma, in the absence of (or at least parallel to) a magnetic field.  Also known as Langmuir or Langmuir-Tonks frequency; see also electrostatic waves, plasma oscillations.  [Source: Plasma Dictionary]

plasma discharge Low-density, low-temperature plasma discharge (such as in a fluorescent light) which, well, glows.  Sputtering in glow discharges is useful in plasma processing of materials.  The voltage applied to the plasma must be greater than the ionization potential of the gas used; most of the plasma voltage drop is near the cathode, where the majority of ionization occurs.  Discharge is sustained by secondary electrons emitted when ions or recombination radiation impact on the cathode; electrons are accelerated away from the cathode and ionize neutral gas in the discharge.  [Source: Plasma Dictionary]

plasma oscillations Class of electrostatic oscillations which occur at/near the plasma frequency (see entry) and involve oscillations in the plasma charge densities.  These modes are also known as Langmuir oscillations or Langmuir waves; in Stix's Waves in Plasmas, they are more properly called Langmuir-Tonks Plasma Oscillations. [Source: Plasma Dictionary]

plasma physics The study of the physical characteristics, properties, and applications of plasmas (see entry above).  Plasma physics encompasses the study of plasmas for industrial use (materials processing and lighting) through much of astrophysics (where most matter is in the plasma state) to fusion energy research.  [Source: Plasma Dictionary]

plasma wave A disturbance of a plasma away from equilibrium, involving oscillations of the plasma's constituent particles and/or the electromagnetic field.  Plasma waves can propagate from one point in the plasma to another without net motion of the plasma.  Terms used to describe the many kinds of waves in plasmas include: Alfven, Circularly Polarized, Cold Plasma, Drift, Electromagnetic, Electron-Cyclotron, Electron Plasma, Electrostatic, Electrostatic Ion, Electrostatic Ion Cyclotron, Evanescent Extraordinary, Ion-Acoustic, Ion Cyclotron, Ion Plasma, Ion Sound, Langmuir, Left Circularly Polarized, Light, Longitudinal, Lower Hybrid, Magnetohydrodynamic (MHD), Magnetosonic, Negative Energy, Nonlinear, Ordinary, Parallel, Perpendicular, Plane, Radio, Right Circularly Polarized, Shock, Space-Charge, Transverse Travelling, Unmagnetized, Upper-Hybrid, Vlasov, Whistler. [Source: Plasma Dictionary

potential In vector calculus, any vector field of a certain type has an associated scalar field called the potential. Potentials find broad applications in physics. In addition to this scalar potential, the vector potential is a related construct. See also scalar potential.  [Source:]

power The time rate at which work is done.  Electrical power is proportional to the product of current and voltage. 

power amplifier (PA) An amplifier which provides high power gain to a wireless transmitter.  Typical figures of merit include gain, efficiency and linearity (in amplitude and phase modulated systems) and stability.  *

power factor The ratio of power to volt-amperes in an alternating current power transmission system.  The cosine of the phase angle between the voltage and current.  When the load is resistive, the power delivered to it is equal to the product of volts and amperes, so the power factor is unity.  When the load is inductive, e.g., an induction motor, the current lags the applied voltage, and the power factor is said to be a lagging power factor. When the load is capacitive, e.g., a synchronous motor or a capacitive network, the current leads the applied voltage, and the power factor is said to be a leading power factor.  Power factors other than unity have deleterious effects on power transmission systems, including excessive transmission losses and reduced system capacity.  Power companies therefore require customers, especially those with large loads, to maintain, within specified limits, the power factors of their respective loads or be subject to additional charges.  [Wikipedia, Federal Standard 1037C]

power (surface) density Radiant power incident on a small sphere, divided by the cross-sectional area of that sphere.

power flux density In radio wave propagation, the power crossing unit area normal to the direction of wave propagation.  Symbol: W Unit: watts per square meter (W/m2).

polyphase AC An electrical current which is generated in two or more phases each having exactly the same the same frequency.  AC power is typically generated and transmitted as 3-phase current.  See also alternating current.

powerline carrier system (PLC) A method of sending information over an electrical power distribution system.  A radio-frequency generator used to impose a high frequency signal on top of the existing distribution voltage sine wave (50-60 Hz).  PLC signals are generally in the 2.5 to 9.5 kHz range, with some older systems operating at 19.5 kHz or higher.

primary winding See transformer

propagation In electrical practice, the travel of waves through or along a medium.  The path traveled by the wave in getting from one point to another is known as the propagation path (such as the path through the atmosphere in getting from a transmitting antenna to a receiving antenna, or the path through the waveguides and other microwave devices in getting from an antenna to a receiver). 

protoscience In the philosophy of science, a protoscience is any new area of scientific endeavor in the process of becoming established.  Sometimes scientific skeptics refer to these endeavors as pathological sciences or, incorrectly, pseudoscience.  Protoscience is a term sometimes used to describe a hypothesis which has not yet been tested adequately by the scientific method, but which is otherwise consistent with existing science or which, where inconsistent, offers reasonable account of the inconsistency. (Source: Wikipedia)

pulse modulated field An electromagnetic field produced by the amplitude modulation of a continuous wave carrier by one or more pulses. 

pulse output power The ratio of (1) the average output power to (2) the pulse duty factor. 

pulse repetition rate The average number of pulses in unit time during a specified period. 

quadrature The state of being separated in phase by 90— (/2 radians).  2. Pertaining to the phase relationship between two periodic quantities varying with the same period, that is, with the same frequency or repetition rate, when the phase difference between them is one-quarter of their period. [Source: Telecommunications: Glossary of Telecommunication Terms

quality factor (Q) In a reactive circuit, the ratio of the reactance in ohms divided by the resistance in ohms.

quantum vacuum Also known as quantum-mechanical vacuum.  Quantum physics reveals that even an ideal vacuum, with a measured pressure of zero Pascals (Pa), isn't really empty.  One reason is that the walls of the vacuum chamber emit light in the form of black-body radiation: visible light if they are at a temperature of thousands of degrees, infrared light if they are cooler.  This soup of photons will be in thermodynamic equilibrium with the walls, and the vacuum can consequently be said to have a particular temperature.  More fundamentally, there are quantum-mechanical fluctuations in the vacuum.  This may be responsible for the observed value of the cosmological constant. [Source: Wikipedia]  (See also Quantum Vacuum, Quantum Vacuum Fluctuations: A New Rosetta Stone of Physics?, Physics of the Quantum Vacuum , The super-particle vacuum, Toward an Explanation: The Quantum Vacuum and Cherenkov radiation in a photon gas

Quasilinear Theory A weakly nonlinear theory of plasma oscillations which uses perturbation theory and the random phase approximation to find the time-evolution of the plasma state. [Source: Plasma Dictionary]

quasineutral plasma A plasma in which positive and negative charges are present in approximately equal numbers, so that there are no strong net electric fields. [Source: Plasma Dictionary]

radiation fields There are three traditional radiation fields in free space as a result of an antenna radiating power.  Near-field, also called the reactive near-field region, is the region that is closest to the transmitting antenna and for which the reactive field dominates over the radiative fields; Fresnel zone, also called the radiating near-field, is that region between the reactive near-field and the far-field regions and is the region in which the radiation fields dominate and where the angular field distribution depends on distance from the transmitting antenna; Far-field, or Rayleigh distance, is the region where the radiation pattern is independent of distance from the transmitting antenna.  When Tesla spoke of the "Hertz wave" he was referring, in essence, to far-field radiation.  See also antenna regions and slow-wave helical resonator.

radiation resistance   The resistance that if inserted in place of the antenna would consume the same amount of power as that radiated by the antenna.  Power consumed by a resistance is equal to the square of the current times the resistance.  Power radiated by an antenna is also proportional to the square of the current, so engineers call the constant of proportionality the "radiation resistance" because they love analogies.  Insofar as measurements at the input to the antenna are concerned, the radiation resistance behaves like an ordinary "ohmic" resistance.  [Antenna input resistance calculation is based upon the input voltage and current.]  Radio engineers like to maximize the radiation resistance [by tuning the antenna structure to resonance and maximizing resonant rise] because that means maximizing the power radiated for a given antenna current.   [This also minimizes reflected power.  Tesla wanted to minimize all resistances in the sphere-to-ground circuit because he wanted to maximize current at the ground connection.  In simple vertical conducting structures, the radiation resistance is proportional to square of the ratio of the height of the structure to the wavelength.  At the low radio frequencies and long wavelengths of interest to Tesla and his contemporaries, this ratio was a small fraction for practical reasons.   For the reasons above, radio engineers wanted to maximize it, and Tesla wanted to minimize it.  Thanks to Henry Bradford

radio A form of wireless communications in which the output of the transmitter takes the form of dissipating electromagnetic radiation which spreads outward from the antenna through free space.  The signal strength drops off as the square of the distance from the source of radiation.  Distant radio receivers have to be very sensitive to detect signals that can measure only a few microvolts per meter in strength. 

radio frequency (RF) The frequencies of the electromagnetic spectrum normally associated with radio wave propagation.  Sometimes defined as any frequency at which transmission of coherent electromagnetic energy radiation is possible.  Any frequency at which electromagnetic radiation is useful for telecommunication.

radio frequency current drive Plasma waves in the radio-frequency range can be used to push resonant plasma particles in such a way that current forms in the plasma; this is a method of non-inductive current drive (see entry) which would allow for steady-state fusion reactors to operate.  See also Radio Frequency Heating, below. [Source: Plasma Dictionary]

radio frequency heating A process for heating plasma by transferring energy to ions or electrons using waves generated by an external oscillator at an appropriate frequency, and propagated into the plasma.  (This is similar to how a microwave oven heats food.) There are various types.   [Source: Plasma Dictionary, see also electron cyclotron heating, ion cyclotron heating, and lower hybrid heating.]

radio frequency interference (RFI) Any induced, radiated, or conducted electrical disturbance or transient that causes undesirable responses or malfunctioning in any electrical or electronic equipment, device, or system.  Same as EMI. 

radio spectrum (See electromagnetic spectrum.)

radio wave 


receiver The portion of a communications system that includes a detector and other circuitry to convert electrical signals (electric waves) to audio or data signals.  It provides reception and, if necessary, demodulation of electronic signals. *

receiving transformer See Tesla receiving transformer

resistive magnetohydrodynamics Also known as non-ideal MHD, this is the branch of magnetohydrodynamics in which the finite resistivity of the plasma is taken into account. [Source: Plasma Dictionary]

resonance A phenomenon exhibited by an electrically excited LC circuit in which a comparatively large oscillatory current flows at a certain frequency.  The change in amplitude as the frequency of the wave approaches or coincides with a natural frequency of the medium.

revisionist science See Historical Revisionism and Stumbling Toward Truth : Fictions of Science 

rotating magnetic field A circular motion from pole to pole the magnetic field in the stator of an ac induction motor.  See also Egg of Columbus

scalar potential Mathematically, a scalar field whose negative gradient is a given vector field.  If the scalar potential is denoted by the Greek letter φ and the vector field it generates as v, then v = -sφThe vector field can be a velocity field or a force field.  Equation (1) therefore means a movement or acceleration towards the direction in which there will be a decrease of potential.  Physically, the scalar potential is similar or identical to potential energy.  Any conservative force field can be represented as the negative gradient of some scalar potential.  Any lamellar field can be represented as having a scalar potential, but a solenoidal field generally does not have a scalar potential (except the degenerate case when it is Laplacian) [Source:

secondary winding See transformer

seismic wave 

self capacitance See internal capacitance.

sensitivity For a receiver, the input signal (in :V or mV) required for a specific output level. The sensitivity of a receiver is taken as the minimum signal level required to produce an output signal having a specified signal-to-noise ratio. *

shock wave A wave produced in any medium (plasma, gas, liquid or solid) as a result of a sudden violent disturbance.  To produce a shock wave in a given region, the disturbance must take place in a shorter time than the time required for sound waves to traverse the region.  The physics of shocks is a fundamental topic in modern science; two important cases are in astrophysics (supernovae) and hydrodynamics (supersonic flight). [Source: Plasma Dictionary]

sky wave The space-wave component of a radio transmission that reaches the receiver by reflection from the ionosphere.

slow-wave helical resonator A quarter wavelength- or one-half wavelength-mode resonant circuit constructed as a single-layer cylindrical inductor wound in the form of a helix (called a solenoid), with capacitive end-loading.  The velocity of a wave disturbance moving along the helix axis is significantly less than that of an electromagnetic wave in free space, making it an inefficient structure for launching space waves (see antenna theory).  A Tesla coil's secondary winding and a magnifying transmitter's base-driven extra coil both behave as slow-wave helical resonators.  For a close-wound coil, the disturbance propagates at an axial velocity of about 0.1% the speed of light in free space.  The axial velocity of the disturbance is established by the pitch of the coil and the speed at which the exciting electrical charge propagates through the wire itself.  See also helical antenna and antenna regions.

soliton or solitary waves Stable, shape-preserving and localized solutions of nonlinear classical field equations, where the nonlinearity opposes the natural tendency of the solution to disperse.  They were first discovered in water waves, and there are several hydrodynamic examples, including tidal waves.  Solitons also occur in plasmas.  One example is the ion-acoustic soliton, which is like a plasma ``sound'' wave; another is the Langmuir soliton, describing a type of large amplitude (nonlinear) electron oscillations.  Solitons are of interest for optical fiber communications, where it has been proposed to use optical envelope solitons as information carriers in fiber optic networks, since the natural nonlinearity of the optical fiber may balance the dispersion and enable the soliton to maintain its shape over large distances. [Source: Plasma Dictionary]

space charge Electrons, protons, and ions moved around in the dielectric of a capacitor by the applied voltage. Charge tends to build up at "discontinuities" in the dielectric, such as the dielectric-electrode interface in film capacitors, at the grain boundaries in crystalline dielectrics, and at various molecular sites simply called "charge traps". Space charge is a major factor in dielectric behavior, such as leakage, high-voltage reliability, and dissipation factor vs. frequency and vs. temperature. Its role in dielectric aging is still the subject of research. Researchers have shown a special interest in cross-linked polyethylene (XLPE) because of its widespread use as a high-voltage insulation in power transmission, but work is also being done with polyethylene napthalate, PMMA, silicon dioxide, and other common dielectrics. Space charge has been extensively studied for many years, but I can—t remember any books or journal articles specifically relating space charge phenomena to capacitor behavior. It may be that capacitor people and dielectric theorists don—t talk to each other much. [Source: CapSite 2006]
     When a metal object is placed in a vacuum and is heated to incandescence, the energy is sufficient to cause electrons to "boil" away from the surface atoms and surround the metal object in a cloud of free electrons. This is called thermionic emission. The resulting cloud is negatively charged, and can be attracted to any nearby positively charged object, thus producing an electrical current which passes through the vacuum. Space charges can also occur within a solid, liquid, or gas dielectric. For example, when gas near a high voltage electrode begins to undergo dielectric breakdown, electrical charges are injected into the region near the electrode, forming space charge regions in the surrounding gas. Space charges can also occur within solid or liquid dielectrics that are stressed by high electric fields. Trapped space charges in solid dielectrics is often a contributing factor for dielectric failures within high voltage capacitors and power cables. [Source: Wikipedia]
In a plasma, a net charge which is distributed through some volume.  Most plasma are electrically neutral or at least quasineutral, because any charge usually creates electric fields which rapidly move surplus charge out of the plasma.  However, in some applications one wishes to apply external electric fields to the plasma, and a net space charge can be produced as a result.  The resulting space charge must often be accounted for in the physics of these sorts of devices. [Source: Plasma Dictionary]

space waves Radio waves or electromagnetic radiation emitted by a 1/2-wave electric dipole antenna in free space.  They can reach the receiver either by ground-wave or sky-wave propagation. 

spectrum The distribution of power versus frequency in an electromagnetic wave.  Often used in the context of frequency allocations in reference to the frequencies allowed for a type of service out of the total available. 

spectrum analyzer An electronic device for automatically displaying the spectrum of the electromagnetic radiation from one or more devices.  A cathode ray tube display is commonly used to display this power-versus frequency spectrum.

Spencer's First Principles 

spurious emission or radiation Far-field electromagnetic radiation transmitted on a frequency outside the bandwidth required for satisfactory transmission of the required waveform.  Spurious emissions include harmonics, parasitic emissions, and intermodulation products, but exclude necessary modulation sidebands of the fundamental carrier frequency.

static fields Electric and magnetic fields that do not vary in intensity or strength with time.

streamer A luminous electrical discharge from a high-voltage terminal traveling out into the surrounding space.  See also arc.

subcarrier A separate analog or digital signal carried on a main radio transmission, which may carry extra information such as voice or data.  It can be an monochromatic unmodulated continuous-wave (CW) signal or an already-modulated signal, which is then modulated into another signal of higher frequency and bandwidth.  This is an established method of multiplexing. (See Wikipedia)

submillimeter The portion of the electromagnetic spectrum between 300 GHz and 1 THz, also known as microwave.  The band exists between the main radio-frequency spectrum and infrared.  Continuum-mode detection is done using specialized heat-sensing detectors called bolometers, which stem from infrared techniques.  Spectral-line measurements, incorporating very high wavelength resolution, use heterodyne receivers somewhat resembling those found in lower-frequency radio receivers.  Such high frequency receivers, approaching 1 Terahertz, are very difficult to manufacture.

Super High Frequency (SHF) The portion of the electromagnetic spectrum between 3 GHz and 30 GHz. 

surface wave see Norton surface wave and Zenneck surface wave.


telautomaton The term which Tesla used to describe his remote controlled boats which were demonstrated in Madison Square Garden in New York City, and also Chicago. Developed principally as an instrument of warfare, this design concept is a direct progenitor of the modern day cruise missile.  It can also be considered as having laid the ground work for robotics and the unmanned exploration of space.

teleforce Tesla's device for projecting concentrated non-dispersive energy by means of a narrow stream of metallic particles.

telegeodynamics Tesla's system for prospecting and the location of underground mineralized structures through the transmission of mechanical energy through the subsurface.  Data from reflected and refracted signals can be analyzed to deduce the location and characteristics of underground formations.  Additional non-mechanical responses to the initial acoustic impulses may also be detected.

terminal capacitance See terminal capacity

terminal capacity A conducting sphere or toroid that is connected to the high voltage terminal of a Tesla coil oscillator, the opposing terminal being grounded.  It is known as an elevated terminal or elevated capacity when the oscillator is configured for use as a wireless transmitter in which case the terminal is mounted on the top of a insulated supporting structure.  A large terminal capacity is illustrated in the patent Apparatus for Transmitting Electrical Energy.  An advanced high potential terminal capable of being charged to 100 million volts is illustrated in Tesla's disclosure "New Art of Projecting Concentrated Non-Dispersive Energy Through Natural Media," circa 1936.  See also high-field emission.

test particle In calculations of plasma parameters such as the Debye Length (see entry) and electrical conductivity, it is often useful to analyze the Coulomb interactions of a sample plasma particle, or test particle, with the rest of the plasma.  Such calculations are then said to use the test particle method. [Source: Plasma Dictionary]

tesla (T) Unit of magnetic flux density equal to 1 weber per meter square or 10,000 gauss.

Tesla antenna A form of wireless antenna or wave launching structure developed by Nikola Tesla in which the transmitted energy propagates or is transferred to the receiver by a combination of electrical current flowing in the ground, electrostatic induction and electrical conduction through plasma with an embedded magnetic field.  See magnifying transmitter, see also Marconi antenna and Hertz antenna.

Tesla coil An electrical oscillator developed by Nikola Tesla which produces high voltage, radio frequency alternating electric current.  In its original form also known as the disruptive discharge coil.  In their first application these devices served as power supplies for experimental high frequency light bulbs and tubes.  They were also used as a source of radio frequency currents in Tesla's pioneering wireless experiments, offering a superior alternative to his high frequency alternators.  The classic Tesla coil consists of an air core transformer with loose coupling between the primary and secondary.  The primary winding is excited by the discharge of a high voltage capacitor through a mechanical switching device known as a "break."  Operation is characterized by a series of individual primary pulses, each being followed by a more rapid series of diminishing secondary oscillations.  The diminishing secondary oscillation is called ring down.  The term —partially-damped wave— is often used in relation to the disruptive discharge Tesla coil.  Vacuum-tube and solid-state Tesla coil (VTTC and SSTC) circuits have been developed in which the break is replaced with an electronic switching device.  This can be a vacuum tube, power transistor, bipolar transistor, power MOSFET, or IGBT.  Typically, these oscillators do not incorporate a primary capacitor, the excitation current being obtained directly from the electrical power supply.  The operation of these oscillators is usually characterized by a rapid series of primary pulses at a rate identical to the resonant frequency of secondary resonator.  The secondary oscillation is refreshed once or twice every cycle, depending on the configuration of the switching circuit.  There is no ring down.  The terms —undamped wave— and "continuous wave" are often used in relation to vacuum-tube and solid-state Tesla coils.  In a properly tuned Tesla coil, the high potential appearing at the secondary's high voltage terminal is developed more or less through a process known as "resonant rise" and exceeds that which would be expected from simple ratio of transformation.  See also disruptive discharge coil and magnifying transmitter.

Tesla coil transmitter A Tesla coil configured specifically for the purpose of wireless transmission of electrical energy using either of two ground-based methods: Ground-Air Conduction and Earth Resonance.  In both cases the Tesla coil oscillator is provided with a robust ground connection and a terminal capacitance that is raised slightly above the top turn of the helical resonator.  The resonator itself has a height-to-diameter aspect ratio of 7:1 to 9:1 or greater.  In the first configuration [type one] a precisely tuned helical resonator receiving transformer must be set in place at a distance in order for the system to function.  In the second [type-two transmitter], a Tesla-coil oscillator and a tuned, unloaded helical resonator are placed in close proximity to each other, each with an independent ground connection.

Theory of operation. The entire earth possesses a naturally existing negative charge or DC electrostatic potential with respect to the conducting region of the atmosphere beginning at an elevation of about 50 kilometers.  The potential difference between the earth and this region is on the order of 400,000 volts.  Near the earth's surface there is a ubiquitous downward directed E-field of about 100 V/m.  In operation, a grounded Tesla coil transmitter creates a local disturbance in this charge.  The disturbance manifests itself as an annular distortion of the background electric field around the transmitters ground terminal.  At a point in time when a measurement of the e-field component of the EM field at the ground terminal shows zero volts above the background potential, other measurements will show it rising in intensity until a point 1/4 wavelength (1/4 λ) away from the ground terminal is reached (axial projection).  From there the e-field diminishes in intensity until, at 1/2 wavelength from the terminal, it again shows zero.  At a measurement point approximately one wavelength away from the ground terminal, an induced e-field once again begins to emerge above the average background field level, again increasing in intensity until a second maxim is reached at 1 1/4  wavelength away from the oscillator.  With a sufficiently powerful transmitter this phenomenon repeats itself over and over until the antipode is reached, at which point reflection takes place and the transmitted energy begins to travel back to its point of origin in the reverse direction.  The elevated terminal of a type-one Tesla-coil transmitter functions as a capacitor plate.  Opposite to this plate is every other electrically conducting body to which it is connected, including the earth and, in some cases, the receiving transformer's elevated terminal.  The transmitter's elevated terminal serves two purposes: first, it acts as a charge reservoir in relation to the earth's surface in the immediate vicinity of the transmitter; second, it is one of two electrodes, the other electrode being the receiving facility's elevated terminal.  The transfer of energy between a type-one transmitter and the requisite receiving transformer is by electrical conduction between the two respective ground terminals, and also between the two elevated terminals.  In a low power system, the propagation of energy between the respective elevated terminals is the result of electrostatic induction or displacement currents, much like the transfer of electrical energy between the plates of a capacitor in an AC circuit.  For a high-power system the coupling between elevated terminals is by electrical conduction through plasma.  The two electrodes act as high voltage discharge terminals for the formation of capacitively coupled discharge plasma with interconnection taking place through the upper level atmosphere.  The ionization of the denser atmosphere directly above the elevated terminals could be facilitated by the use of an ionizing beam of ultraviolet radiation to form what might be called a high-voltage plasma transmission line.  In the operation of a type-two system, the ground between the driven oscillator and the nearby helical resonator is incorporated as a part of the transmitter.  As a result, a powerful current flows through the earth between the two ground terminals.  Coupling between the transmitter's two elevated terminals is by electrical conduction through plasma.  There is also some magnetic inductive coupling between the two helical resonators.  As a result, an electrical disturbance is impressed upon the earth.  This can be detected —at great distance, or even all over the surface of the globe— [On Light and Other High Frequency Phenomena].  See also Tesla Effect

Tesla Effect The wireless transmission of electrical energy between a Tesla coil transmitter and a Tesla receiving transformer by the means of electrical currents.  These currents flow through the earth between the two ground terminals, and through the air or upper half space between the two elevated terminals.  The current flowing between the elevated terminals can be a combination of both electrostatic induction or displacement current and electrical conduction through plasma.  A disturbance of the earth's naturally existing negative charge may also be involved.  In the case of a high power system the current flow between the elevated terminals is entirely by electrical conduction through plasma.  The plasma may contain an embedded magnetic field. The energy transfer does not involve electromagnetic radiation or radio waves as defined in the narrowest sense of the terms, that is, far-field electromagnetic waves that have closed back upon themselves with their E and H components in phase, and are no longer associated with accelerating and decelerating charge carriers in the launching structure.  (These are the "Hertz waves" to which Tesla occasionally refers in his writings.)  While radio waves are not directly involved with the transmission of energy between the transmitter and the receiver, they do constitute a mechanism for the loss of electrical energy from the entire resonating system comprised of these two electrically connected elements.

Tesla receiving transformer A grounded resonance transformer specifically intended for the reception of energy transmitted by a Tesla coil transmitter.  The apparatus consists of a vertical helical resonator, the transformer's primary winding, with the bottom terminal connected to ground and the top terminal an elevated terminal capacity.  Tuning is accomplished by modifying either the height or surface area of the elevated terminal, and adjusting the value of a small self inductance inserted into the antenna circuit at the bottom of the resonator.  A relatively short secondary winding may be positioned in close proximity around the bottom portion of the resonator.

Tesla turbine A rotary engine consisting of multiple ported disks which are mounted in parallel on a shaft and placed within a cylindrical casing.  In operation high velocity gases enter tangentially through a wide nozzle at the periphery of the disks, flow between them in free spiral paths to exit through central exhaust ports.  The slight viscosity of the gas along with its adhesion to the faces of the disks combined to efficiently transfer the fuel's energy to the disks and on to the shaft.

time-varying fields Electric and magnetic fields that change in intensity or strength with time. Examples include 60 Hz, modulated, and transient fields.

total dynamic head (TDH) When a pump is lifting or pumping water, the vertical distance from the elevation of the suction side of the pump to the elevation of the discharge side of the pump.  The total dynamic head is the static head plus pipe friction losses.  Static head is the vertical distance between water surfaces when the water is not moving.

transformer An electrical device consisting of two or more coils of wire placed in close proximity to each other.  An alternating current applied to the first coil or "primary" sets up a time varying magnetic field which transfers energy to the "secondary" winding(s) by electromagnetic induction.  Commonly used to increase or decrease voltage levels in power supply circuits.  Also used for the purpose of coupling within audio and RF circuits.

transient  A high-voltage surge or spike in an electrical transmission system caused by lightning strikes to nearby transformers, overhead lines, or the ground, and which may persist for a relatively short time after the phenomenon (sometimes called ringing).  They may also result from the switching of motors, short circuits, or utility system switching.

transmitter Equipment which generates RF power to be fed to an antenna or other output interface for transmission.  In modern radio equipment it consists of active components such as a modulator, driver and PA and passive components such as a TX filter.  Taken together, these components impress an information carrying signal onto an RF carrier of the correct frequency by instantaneously adjusting its phase, frequency, or amplitude and provide enough gain to the signal to project it through the ether to its intended recipient.  *

transmission line The material medium or structure that forms all or part of a path from one place to another for directing the transmission of energy, such as electric currents, magnetic fields, acoustic waves, or electromagnetic waves.  Examples of transmission lines include wires, optical fibers, coaxial cables, rectangular closed waveguides, and dielectric slabs.  The electrical conductor that connects a transmitter or receiver to an antenna.  Usually coaxial cable or sometimes twin lead consisting of two parallel conductors.  Also known as a feedline.

transport, in plasmas The problem of understanding the motions of particles in a plasma (and the related flows of energy, momentum, and other physical quantities) is extremely important in many if not all areas of plasma research.  The theory of transport in plasmas is highly complex, but an understanding of transport is vital to controlled fusion research (where insufficient energy confinement is a major obstacle to producing fusion energy), plasma astrophysics (where radiation transport through plasmas often plays a dominant role), and many other areas including high energy-density plasmas, plasma processing of materials, space plasmas, and more.  Since plasmas are many-body systems, it is not possible to follow all 6 degrees of freedom of each particle in the plasma, and consequently statistical methods and fluid theories must be employed, though even these often prove barely tractable for realistic situations.  The wide variety of possible plasma conditions (spanning over 30 orders of magnitude in density and over 6 orders of magnitude in temperature) leads to a wide range of phenomena, including flows, turbulence, waves and nonlinear wave-particle interactions, and shocks.  Specific approximations are generally needed to treat specific classes of plasma conditions over specific time and distance scales.  Some key topics in plasma transport research include the determination of transport coefficients such as viscosity and diffusivity, and related parameters such as electrical conductivity and particle and energy confinement times. [Source: Plasma Dictionary]

Ultra High Frequency (UHF) The portion of the electromagnetic spectrum between 300 MHz and 3 GHz.

Ultra Low Frequency (ULF) The portion of the electromagnetic spectrum below 3 Hz

undamped wave See continuous wave.

Van de Graaff generator An electrostatic generator used to produce high voltage DC, consisting of a large spherical terminal mounted on a hollow insulating support.  An endless motor-driven dielectric belt runs through the support from the base to the pulley within the terminal.  In the machine, charge is sprayed by point discharge from metal needles, held at a potential of about 10 kV, on to the bottom of the belt.  A row of needles near the upper belt pulley removes the charge from the belt and passes it to the outer surface of the spherical terminal.  Tesla designed a Van de Graaff generator in which the belt was replaced by desiccated air circulated by a disk-type blower.

Very High Frequency (VHF) The portion of the electromagnetic spectrum between 30 MHz and 300 MHz.

Very Low Frequency (VLF) The portion of the electromagnetic spectrum between 3 kHz and 30 kHz.

violet ray device An electrical appliance intended for the physical application of high potential, high frequency electrical current for electrotherapeutic purposes. It consists of two elements, a Tesla coil transformer assembly and a gas filled electrode. These instruments were very popular in the early part of the 20th century and were widely marketed.  While the efficacy of the device has been disputed, it is said to work by stimulating blood circulation. [See also Violet Ray Generators

Volt-Amp Reactive (VAR) 

Voltage Standing-Wave Ratio (VSWR) or SWR  The ratio of the forward voltage to reflected voltage on a transmission line in an antenna system.  A VSWR of 1:1 occurs when all parts of the antenna system are matched correctly to one another.  When a transmission line is terminated with an impedance, Zx, that is not equal to the characteristic impedance of the source and the transmission line, Zo, not all of the incident power is absorbed by the termination.  Part of the power is reflected back to the generator so that phase addition and subtraction of the incident and reflected waves create a voltage standing wave pattern on the transmission line.  The ratio of the maximum to minimum voltage is known as the Voltage Standing Wave Ratio (VSWR) and successive maxima and minima are spaced by 180— (/2).

Wardenclyffe Nikola Tesla's historic laboratory and wireless communications facility located about 65 miles east of New York City on the North Shore of Long Island. It was here that he worked out many of the final details for his "World System." Although the distinctive 187 foot tall tower was demolished in 1917, the sturdy 94 foot square building still stands in silent testimony to Tesla's unfulfilled dream.

Watt A measurement unit of electrical ability to perform work.

wave Propagation of disturbances from place to place in a regular and organized way.  Most familiar are surface waves that travel on water, but sound, light, and the motion of subatomic particles all exhibit wavelike properties.  In the simplest waves, the disturbance oscillates periodically (see periodic motion) with a fixed frequency and wavelength.  Mechanical waves, such as sound, require a medium through which to travel, while electromagnetic waves (see electromagnetic radiation) do not require a medium and can be propagated through a vacuum.  Propagation of a wave through a medium depends on the medium's properties.  (Britannica Concise Encyclopedia, 2004)

waveguide A material medium that confines and guides a propagating electromagnetic wave.  In the microwave regime, a waveguide normally consists of a hollow metallic conductor, usually rectangular, elliptical, or circular in cross section.  This type of waveguide may, under certain conditions, contain a solid or gaseous dielectric material.  In the optical regime, a waveguide used as a long transmission line consists of a solid dielectric filament (optical fiber), usually circular in cross section.  In integrated optical circuits an optical waveguide may consist of a thin dielectric film.  In the rf regime, ionized layers of the stratosphere and refractive surfaces of the troposphere may also act as a waveguide.

wavelength () The distance traveled by a wave in one period (the period is the time required to complete one cycle).  = c / f.  In the atmosphere, electromagnetic waves travel at c, the speed of light (300 million meters per second or 30 cm/nsec).  At 100 kHz, one wavelength = 3000 meters, at 15 MHz, one wavelength = 20 meters.  5 GHz, one wavelength = 6 cm.  The distance between two successive points of a periodic wave in the direction of propagation, in which the oscillation has the same phase.

wave-meter An instrument for measuring the frequency of a radio wave.  The wave-meter is a mechanically tunable resonant circuit.  Below 20 GHz, the wave-meter has been replaced by the frequency counter with much greater accuracy and ease of use.

weber Unit of magnetic flux equal to the flux linking a single turn of wire, which produces in the wire an electromotive force of 1 volt when reduced to zero in 1 second.  (mks).  See also gauss and tesla.

whistler A plasma wave which propagates parallel to the magnetic field produced by currents outside the plasma, at a frequency less than that of the electron cyclotron frequency, and which is circularly polarized, rotating about the magnetic field in the same sense as the electron gyromotion.  The whistler is also known as the electron cyclotron wave.  The whistler was discovered accidentally during World War I by large ground-loop antennas intended for spying on enemy telephone signals.  Ionospheric whistlers are produced by distant lightning, and get their name because of a characteristic descending audio-frequency tone, which is a result of the dispersion relation for the wave: lower frequencies travel somewhat slower, and therefore arrive at the detector later. [Source: Plasma Dictionary]

wireless Any system by which electrical energy is transmitted without wires from one location to another.  The three principle methods are electrical induction, electromagnetic radiation, electrical conduction.  The induction method involves the coupling of two widely separated loops of wire in much the same way as the primary and secondary windings of a transformer are linked.  In the present system that we now know as "radio" the propagation of energy takes place by electromagnetic radiation. The third method—ground conduction—bears a great similarity to radio in that in both cases the transmitting element incorporates a radio frequency electrical oscillator. The difference exists in the fact that in the latter case the transmitter's output signal is sent to an underground connection rather that an elevated antenna.

wire gauge See American Wire Gauge

World System Tesla's plan for a system to provide global wireless broadcasting, telecommunications, and a long range aid to navigation.  In its more developed state he envisioned the system would include electrical power distribution.  In practical application, the physical mechanism includes at least two large magnifying transmitters.  It has been suggested that magnetohydrodynamics can be used to model the operation of the system.

WRC World Radio Conference

X ray 

Zenneck surface wave A low frequency transverse magnetic surface wave that travels along the interface between the ground and the air, in which the propagating energy does not radiate into space but is concentrated near the guiding surface.  These waves do not contribute significantly to the field produced by a conventional dipole or quarter-wave radiator, however they can be strongly excited by a grounded quarter-wave helical resonatorSee slow-wave helical resonator and magnifying transmitter.

Geometry for Zenneck wave propagation.

The complex longitudinal propagation phase constant along the Earth's surface.

Zenneck wave field strength decrease for around-the-world propagation as a function of frequency in kHz.  [*]

* Corum, K.  L.  and J.  F.  Corum, "The Zenneck Surface Wave," Appendix II of "Nikola Tesla, Lightning Observations, and Stationary Waves," 1994.

Additional Glossaries:
Federal Standard 1037C, Glossary of Telecommunications Terms 

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