18WuD2x

626 short-skip communication • SI
short-skip communication Radio communication
via the ionosphere over relatively short distances
(400 to 1300 miles). See, for example,
SPORADIC-E SKIP.
short-term drift The gradual change in the value
of a quantity, such as frequency or voltage, observed
over a comparatively brief interval, as opposed
to change occurring over a long period.
Compare LONG-TERM DRIFT.
short-term effect The variation of any electrical
parameter over a relatively brief time interval. Example:
frequency drift over a short time period.
Also called short-time effect.
short-term stability Stability reckoned over a
comparatively brief time interval, as opposed to
stability for a long period. Compare LONG-TERM
STABILITY.
short-time effect See SHORT-TERM EFFECT.
shortwave 1. Pertaining to wavelengths shorter
than 200 meters (i.e., frequencies higher than
1.50 MHz). 2. Pertaining to the frequencies above
the standard amplitude-modulation broadcast
band (above 1.605 MHz), but below 30 MHz.
shortwave converter A superheterodyne converter
for adapting a longwave receiver (such as a
broadcast receiver) for shortwave reception.
shortwave listener Abbreviation, SWL. A radio
hobbyist who receives, but does not transmit,
shortwave signals.
shortwave receiver Any radio receiver capable of
intercepting and demodulating signals in the
range 1.705 MHz to 30 MHz.
shortwave transmitter Any radio transmitter capable
of producing energy in the range 1.705 MHz
to 30 MHz.
shot-effect noise Electrical noise caused by random
fluctuations in a current, as in a diode or
transistor. Also see EQUIVALENT NOISE RESIS-
TANCE. Compare THERMAL NOISE.
shotgun microphone A highly directional microphone
sensitive only to sounds coming from a
specific direction; the response pattern has a narrow
main lobe. It name results from its long,
cylindrical configuration.
shot noise Electrical noise arising from intermittent
impulses, such as those produced by spark
discharges, make-and-break contacts, etc. Its
name results from its resemblance to pistol shots.
shrink The amount by which a material being measured
with an electronic instrument decreases in
surface dimension. Compare STRETCH.
shrink tubing Plastic sleeving placed over a conductor
or at a conductor/connector joint, and
made to shrink tightly with the application of
heat.
shunt Synonym, parallel. 1. Pertaining to the
connection of one component across (in parallel
with) another (e.g., shunt resistor). 2. Pertaining
to connection of components in such a manner
that they each (or all) are subjected to identical
voltages. 3. A deliberately produced short circuit
between two specific points in a device or system.
4. To deliberately bypass some part of a system
by means of a short circuit.
shunt circuit See PARALLEL CIRCUIT.
shunt-diode rectifier A rectifier circuit in which
the diode is connected in parallel with the source
and load. Compare SERIES-DIODE RECTIFIER.
shunt-fed 1. Pertaining to a circuit or device in
which the direct-current operating voltage and alternating-current
signal voltage are applied in
parallel to an electrode. 2. Pertaining to a basegrounded
vertical antenna excited at some point
above ground.
shunt feed See PARALLEL FEED.
shunt feedback A feedback system in which the
fed-back signal is presented to the input of the
network in parallel with the input signal. Compare
SERIES FEEDBACK.
shunt generator An electric generator in which the
armature and field windings are connected in
parallel. Compare SERIES GENERATOR.
shunting effect The condition in which a quantity,
such as stray capacitance or resistance, acts in
parallel with another quantity. Example: the
shunting (parallel) resistance of an electrolytic
capacitor.
shunt leads Interconnecting wires used for the
purpose of attaching a shunting component to a
test instrument.
shunt limiter See PARALLEL LIMITER.
shunt loading The parallel insertion of reactance
in a circuit, for the purpose of impedance matching.
shunt motor An electric motor whose armature
and field windings are connected in parallel.
Compare SERIES MOTOR.
shunt regulator A voltage-regulator circuit in
which the controlled transistor or vacuum tube is
in parallel with the output (load) terminals. Compare
SERIES REGULATOR.
shunt resistor 1. A resistor connected in parallel
with a meter or recorder to increase its current
range. 2. A resistor connected in parallel with a
voltmeter to convert it into a current meter. Compare
MULTIPLIER RESISTOR.
shunt-series circuit See PARALLEL-SERIES CIR-
CUIT.
shunt tee junction A waveguide H-PLANE TEE
JUNCTION.
shunt-type frequency multiplier A varactor frequency
multiplier circuit in which the varactor is
in parallel with the input and output. Compare
SERIES-TYPE FREQUENCY MULTIPLIER.
shunt-type resonance bridge A resonance bridge
in which the impedance arm is a parallel-resonant
circuit. Compare SERIES-TYPE RESO-
NANCE BRIDGE.
shunt-wound generator See SHUNT GENERATOR.
shunt-wound motor See SHUNT MOTOR.
SI Abbreviation of (Standard) INTERNATIONAL
SYSTEM OF UNITS.