18WuD2x

ar meter • baseband frequency response 63
disadvantage is that it does not provide a precise
indication.
barn Symbol, b. A non-SI unit of nuclear cross section
equal to 100 square femtometers or 10 – 24
square centimeters. This unit is approved as
compatible with SI (International System of
Units).
Barnett effect The development of a small amount
of magnetization in a long iron cylinder that is rotated
rapidly about its longitudinal axis.
barograph A recording barometer, using either a
drum recorder (pen recorder) or a computer to
store the data as a function of atmospheric pressure
versus time.
barometer An instrument for measuring atmospheric
pressure.
barometer effect A relation that appears to exist
between the intensity of cosmic rays and the atmospheric
pressure. It is an inverse relation; that
is, increasing pressure seems to correlate with reduced
intensity of cosmic rays. It is said to be approximately
to 1 or 2% per centimeter of mercury.
barometric pressure The atmospheric pressure,
usually given in inches of mercury. The average
barometric pressure at the surface of the earth is
just under 30 inches of mercury.
bar pattern A series of spaced lines or bars (horizontal,
vertical, or both) produced on a television
picture screen by means of a BAR GENERATOR.
It is useful in adjusting horizontal and vertical
linearity of the picture.
barrage array An antenna array in which a string
of collinear elements are vertically stacked. The
end quarter wavelength of each string is bent in
to meet the end quarter wavelength of the opposite
radiator to improve balance.
barrage jamming The jamming of many frequencies,
or an entire band, at the same time.
barrell distortion Television picture distortion
consisting of horizontal and vertical bulging.
barrier 1. The carrier-free space-charge region in a
semiconductor pn junction. 2. An insulating partition
placed between two conductors or terminals
to lengthen the dielectric path.
barrier balance The state of near equilibrium in a
semiconductor pn junction (after initial junction
forming), entailing a balance of majority and minority
charge carrier currents.
barrier capacitance 1. The capacitance in a bipolar
transistor between the emitter and collector. It
varies with changes in applied voltage, and also
with the junction temperature. 2. The capacitance
across any pn junction that is reverse-biased.
barrier height The difference in voltage between
opposite sides of a barrier in a semiconductor
material.
barrier layer See BARRIER, 1.
barrier-layer cell A photovoltaic cell, such as the
copper oxide or selenium type, in which photons
striking the barrier layer produce the potential
difference.
barrier potential The apparent internal dc potential
across the barrier (see BARRIER, 1) in a pn
junction.
barrier strip A terminal strip having a barrier (see
BARRIER, 2) between each pair of terminals.
barrier strip
barrier voltage The voltage required for the initiation
of current flow through a pn junction.
Bartlett force See EXCHANGE FORCE.
baryon A subatomic particle made up of three
quarks.
base 1. In a bipolar transistor, the intermediate region
between the emitter and collector, which
usually serves as the input or controlling element
of transistor operation. 2. A substance that dissociates
in water solution and forms hydroxyl
(OH) ions. For example, sodium hydroxide. 3. The
constant figure upon which logarithms are computed
(10 for common logs, 2.71828 for natural
logs). 4. The radix of a number system (e.g., base
10 for the decimal system, base 8 for the octal
system, base 16 for the hexadecimal system, and
base 2 for the binary system). 5. A fixed nonportable
radio communications installation.
base address The number in a computer address
that serves as the reference for subsequent address
numbers.
baseband The frequency band of the modulating
signal in a communications, broadcast, or data
transmitter. For voice communications, this is
generally the range of voice frequencies necessary
for intelligible transmission. For high-fidelity music
broadcasting, it is approximately the range of
human hearing. For fast-scan television, it
ranges up to several megahertz. It can be restricted
or expanded, depending on the nature of
the transmitted signal. See BASEBAND FRE-
QUENCY RESPONSE.
baseband frequency response 1. The amplitudeversus-frequency
characteristic of the audiofrequency
(AF) or composite video section of a
transmitter that defines the BASEBAND, or range
of modulating frequencies. 2. The range of frequencies
over which a radio transmitter can be
modulated to convey information. For single sideband
(SSB), it is approximately 300 Hz to 3 kHz;
for high-fidelity, frequency-modulated (FM) music