18WuD2x

hard wiring • harmonic-distortion percentage 331
hard wiring 1. In computer systems, functions or
programs built directly into the machine hardware.
In order to alter such functions or programs,
the system wiring and/or components
must be physically changed. 2. A system interconnected
entirely by wires and cables, and using
no free-space links, such as radio or infrared.
hard X rays High-frequency (shortwave) X rays.
Such radiation has high penetrating power. Compare
SOFT X RAYS.
harmonic 1. Symbol, H. In a complex sound or signal
wave, a component whose frequency is a multiple
of the FUNDAMENTAL FREQUENCY by a
whole-number factor of 2 or more. 2. Pertaining
to whole-number multiples of the FUNDAMEN-
TAL FREQUENCY of a sound or signal, as defined
in 1.
Amplitude Amplitude
Third
harmonic
wave
Fundamental wave
Fundamental pip
Second harmonic wave
A
Second
harmonic
pip
Frequency
B
Third
harmonic
pip
Fourth
harmonic
wave
Fourth
harmonic
pip
harmonic: waves (A)
and spectrum-analyzer display (B)
Time
harmonic accentuation Increasing the amplitude
of harmonic components in a complex wave using
filters, amplifiers, or special modes of operation.
harmonic accentuator A circuit or device, such as
a harmonic amplifier or bandpass filter, for emphasizing
signal harmonics.
harmonically related bands In communications,
frequency bands arranged so that the frequencies
in one band are harmonics of the frequencies in
another band. An example of bands that are precisely
related in this way are 4.1 to 4.3 MHz and
8.2 to 8.6 MHz. Various amateur radio bands are
harmonically related to some extent, such as 40
meters (7.0 to 7.3 MHz) and 20 meters (14.0 to
14.35 MHz).
harmonic amplifier An amplifier, such as one
used with a frequency standard, used to increase
the amplitude of weak harmonics. Also see HAR-
MONIC ACCENTUATION.
harmonic analysis 1. The evaluation of the harmonic
content of a complex wave. See, for example,
HARMONIC WAVE ANALYZER; SCHEDULE
METHOD, 2; SPECTRUM ANALYZER; and WAVE
ANALYZER. 2. See FOURIER ANALYSIS.
harmonic analyzer See HARMONIC WAVE ANA-
LYZER, SPECTRUM ANALYZER, and WAVE ANA-
LYZER.
harmonic antenna An antenna operated at a harmonic
of the lowest frequency at which it is resonant.
For example, a half-wave dipole cut for 7.0
MHz, but used for transmitting and receiving at
21.0 MHz, is functioning at the third harmonic.
harmonic attenuation Reduction of the amplitude
of harmonic components in a complex wave using
filters, tuned amplifiers, or special modes of operation.
harmonic attenuator A circuit, device, or method
of operation (such as a filter, tuned amplifier,
special biasing, or special bypassing) for reducing
the amplitude of harmonics.
harmonic component See HARMONIC.
harmonic composition See HARMONIC DISTRI-
BUTION.
harmonic content The amount of harmonic
energy present in a complex wave. Also see
HARMONIC-DISTORTION PERCENTAGE and
HARMONIC RATIO.
harmonic-cut crystal Also called overtone crystal.
A quartz crystal that, when operated in the
proper circuit, oscillates at a harmonic of the
(fundamental) frequency dictated by its thickness.
harmonic detector A detector tuned to respond to
a harmonic of a signal.
harmonic distortion 1. The generation of harmonics
by the circuit or device by which the signal
is processed. 2. The deformation of the
original signal that results from the action described
in 1. 3. The disproportionate reproduction
of a signal’s harmonic components.
harmonic distortion meter See DISTORTION ME-
TER.
harmonic-distortion percentage In a signal containing
harmonics, the harmonic energy as a percentage
of the total signal energy (fundamental
plus all harmonics). Also called total harmonic
distortion (THD).