18WuD2x

640 software • soldering gun
or computer system. 2. The detailed instructions
for performing a particular operation with a calculator
or a computer.
software-defined radio Abbreviation, SDR. 1.
Wireless communications in which the modulation
waveforms and protocols are generated and
decoded by computer software. This allows a
single, microcomputer-controlled radio receiver,
transmitter, or transceiver to operate in a variety
of services that use different protocols. Changing
the modulation waveform or protocol requires
only a change in the program run by a microcomputer
that controls the radio. 2. A receiver,
transmitter, or transceiver that employs the
technology defined in (1). 3. The use of wireless
equipment that employs the technology defined
in (1).
soft X rays Low-frequency (long-wavelength)
X rays. Such radiation has relatively poor penetrating
power. Compare HARD X RAYS.
sol 1. Abbreviation of SOLUTION. 2. Abbreviation
of SOLUBLE.
solar access For a specific property or location, the
availability of direct exposure to the sun’s rays as
a source of energy.
solar absorption index A quantitative measure of
the effect of the sun on the ionospheric absorption
of radio waves.
solar activity See SOLAR RADIATION and
SUNSPOT cycle.
solar battery A battery composed of solar cells
connected in series and/or parallel for increased
output.
solar cell A photovoltaic power transducer that
converts visible light to electricity. It is called a
cell because its output is a low direct-current
voltage. Such cells can be connected in series
and/or parallel to provide useful electric power
output.
solar cycle See SUNSPOT CYCLE.
solar energy 1. The total energy arriving from the
sun, over a given period of time and within a specific
surface area, at a given location on the surface
of the earth. 2. Any energy derived entirely
from the sun.
solar-energy conversion Any process that changes
solar radiant energy into another useful form.
solar flare
A violent storm on the surface of the
sun. These events tend to occur near the peak of
the 11-year sunspot cycle. They cause an increase
in the level of radio noise that comes from
the sun, and they emit high-speed subatomic
particles that reach earth a few hours after the
first appearance of the flare. Because the particles
are electrically charged, they are accelerated
by the geomagnetic field. Sometimes a geomagnetic
storm results, producing aurora near the
poles and deterioration of ionospheric radiopropagation
conditions.
solar flux An indicator of general solar activity. The
solar noise level is measured at a particular frequency,
such as 2800 MHz. The solar flux tends to
be highest during periods of the greatest sunspot
activity and immediately following a solar flare.
solar laser See SUNLIGHT-POWERED LASER.
solar noise Broadband electromagnetic noise generated
by the sun. In particular, noise that occurs
at radio frequencies and affects satellite, moonbounce,
and space communications. This noise
varies in intensity with the 11-year sunspot cycle,
being generally higher at and near sunspot maxima.
A solar flare can cause a sudden and dramatic
increase in the noise at all wavelengths.
See SOLAR FLARE.
solar panel An array consisting of a number of series-connected
or series-parallel-connected solar
cells mounted on a flat plate.
solar power Useful amounts of electricity obtained
from suitable arrays of solar cells.
solar radiation Electromagnetic energy of various
wavelengths originating in the sun. Such radiation,
after passing through the earth’s atmosphere,
consists mostly of infrared rays and
visible light. Some ultraviolet rays also reach the
earth’s surface.
solar relay See SUN SWITCH.
solar switch See SUN SWITCH.
solar wind Continuous emission of high-speed subatomic
particles by the sun. It causes distortion of
the lines of flux in the earth’s magnetic field. It becomes
more intense following a solar flare.
solder
1. A metal alloy (usually of tin and lead) that
is melted to electrically and mechanically join
pieces of other metals. Also see HARD SOLDER
and SOFT SOLDER. 2. To join metals with solder.
solder
Solder Melting point Principal
type (°F/°C) uses
Tin-lead 50 : 50, 430/220 Electronic
rosin-core
circuits
Tin-lead 60 : 40, 370/190 Electronic
rosin-core
circuits,
low-heat
Tin-lead 63 : 37, 360/180 Electronic
rosin-core
circuits,
low-heat
Tin-lead 50 : 50, 430/220 Non-electronic
acid-core
metal bonding
Silver 600/320 High-current,
high-heat
soldering Joining (usually nonferrous) metal parts
with solder, a lead-alloy substance. Compare
BRAZING.
soldering gun An electric soldering iron having the
general shape of a handgun. The element heats
and cools more rapidly than the element in a