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Key Terms - MNOP

Magnetic Shield (H-field)An induction field caused predominantly by a current source. Also called a low impedance source, such as may be generated by a loop antenna. This level is expressed in dB, with respect to a reference level or as amperes per meter in absolute units
Magnetic Loop A magnetic field loop antenna, usually a 12 inch diameter loop with the number of turns of wire varies the useful frequency range (low impedance)
MaskingAn increase in the threshold of audibility of a sound necessary to permit its being heard in the presence of another sound 
Mass Law An approximation that describes the Sound Transmission Loss (STL) of a limp, flexible barrier in terms of mass density and frequency. For each doubling of the weight or frequency of a partition, Mass Law predicts a 6 dB increase in STL. The Mass Law provides rough estimates of STL for single wall structures; however, deviations from laboratory-measured results may be 10 dB or more. For double wall or other complex structures, the Mass Law does not apply
Max Hold A mode of acquisition for a digital storage system where maximum amplitude achieved at every frequency being analyzed is retained and continuously displayed for successive sweeps
Max Span A mode of operation in which the spectrum analyzer scans an entire frequency band
Maximum Input Maximum amount of power capable of being handled by the circuitry of an instrument without damage
Milligauss (mG) A unit of magnetic flux density; 1mG = 0.001 gauss
Motor Generator Electric motor driving an AC generator. Used to provide clean, regulated AC power for electronic loads
Monopole An electric field (high impedance) rod antenna usually 41 inches high
Multipoint Ground More than one path to ground

Nano Tesla (nT) A unit of magnetic flux density; 1nT = 10 E-9 Tesla or 10 E-5 Gauss
Near Field/Induction The area before the transition of the electric and magnetic field where the electric field impedance is high and the magnetic field impedance is low. In the near field electric and magnetic fields must be treated independently
Noise Unwanted disturbances superimposed upon a useful signal that tend to obscure its information content
Noise Floor The instrument noise level determined by the resolution bandwidth
Nosie Sideband Undesired response caused by noise internal to the spectrum analyzer appearing on the display around a desired response

Octave A term that means to double the frequency
Octave BandsFrequency ranges in which the upper limit of each band is twice the lower limit. Octave bands are identified by their geometric mean frequency or center frequency
OhmUnit of electrical resistance
One-Third Octave Bands Frequency ranges where each octave is divided into one-third octaves with the upper frequency limit being 2 1/3 (1.26) times the lower frequency. Identified by the geometric mean frequency of each band.
Open As in "open circuit" i.e: no current flow between two conducting surfaces
 Maximum measurable ground isolation of an enclosure
  Maximum resistance, usually beyond the range of the ohmmeter
Parallel The orientation for magnetic loop antennas per NSA-65-6. Oriented with the loops in a position parallel to the shield
Passive Device A component that does not provide rectification, amplification, or switching, but reacts to voltage and current
PermeabilityThe ability of a material to carry magnetism, compared to air which has permeability of one. The capability of a material to be magnetized at a given rate. It is a non-linear property of both the magnetic flux density and the frequency of wave propagation
Phase LockThe control of an oscillator, so as to operate at a constant phase angle relative to a stable reference signal source. Primary use in analyzers is for frequency stability of oscillators
Pink Noise Broadband noise whose energy content is inversely proportional to frequency
Planewave A far field wave which exists at a distance greater than the wavelength divided by 2π from the source, where the impedance of the wave is nearly equal to the impedance of free space (377 ohms)
PowerThe time rate at which work is done. Power is expressed in watts
PropagationThe travel of waves through or along a medium. A wave may propagate thru a wire, thru air or space, or thru a pipe or waveguide
 A wave whose shape conveys some intelligence, message or effect
 The transfer of energy by electromagnetic radiation at radio frequencies

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