18WuD2x

90 bulk effect • burst generator
tive resistance of all paths around the junction,
through the mass of the wafer). Compare SUR-
FACE EFFECT.
bulk-erased tape Recording tape whose signal
content has been removed via a bulk eraser.
bulk-erase noise 1. The residual magnetic impulses
that remain on a magnetic tape after it has
been bulk-erased. 2. Noise generated by bulkerased
tape when the latter passes through deenergized
record or erase heads in a tape machine.
bulk eraser A type of power-line-frequency degausser
that erases an entire reel of magnetic
tape without requiring that the tape be unreeled
and passed continuously under an erase head.
This saves considerable time, but often leaves
some BULK-ERASE NOISE on the tape. Also
called BULK DEGAUSSER.
bulletin board In personal computing or amateur
packet communications, a system that allows
subscribers to leave messages for each other for
access via a modem or terminal node controller.
bulletin station A station intended for the transmission
of bulletins of interest to certain parties,
such as military personnel or amateur radio operators.
An example is W1AW in Newington, Connecticut,
an amateur radio station that transmits
bulletins and code practice.
buncher In a Klystron, a cavity resonator that contains
two grids mounted parallel to the electron
stream. The electrostatic field of the grids alternately
accelerates and retards the electrons, velocity-modulating
the stream into bunches.
buncher grids In a Klystron, the closely spaced
grids that velocity-modulate the electron beam
into successive bunches.
buncher resonator In a velocity-modulated tube,
such as a Klystron, the input cavity resonator.
buncher voltage The radio-frequency (RF) grid-togrid
voltage in the buncher resonator of a
Klystron.
bunching The production of electron bunches in a
velocity-modulated tube, such as a Klystron. Also
see BUNCHER.
bunch stranding A technique for combining several
thin wires into a single thick wire. Often used
in guy wires and electrical conductors to improve
tensile strength and flexibility. At radio frequencies,
bunch stranding also improves electrical
conductivity by increasing the ratio of surface
area to cross-sectional area. This minimizes
losses caused by skin effect.
Bunet’s formula A formula for calculating the inductance
of a multilayer air-core coil that has a
diameter less than three times the length:
L = a 2 N 2 /(9a + 10l + 8.4c + 3.2cl/a)
where N is the number of turns, a is the average
coil radius, c is the winding thickness, and l is the
length of the coil.
Bunsen cell A cell consisting of a zinc rod in a sulfuric
acid solution contained in a porous pot,
which is in a nitric acid solution. The zinc rod
serves as the negative pole; the positive pole is a
piece of hard carbon. The cell produces about 1.9
volts and delivers relatively high current.
See VOLTAGE BURDEN.
burden
burn 1. A blemish on the screen of a cathode-ray
tube (CRT), caused by destruction of the phosphor
there. This results from prolonged focusing
of an intense electron beam in one spot. 2. A
blemish on the screen of a television picture tube,
usually resulting from ions that reach the screen
when the ion trap is not working correctly.
burn-in
A long, thorough, carefully controlled preliminary
test of a component, device, or system,
to stabilize its electrical characteristics after
manufacture and to ensure that it will function
according to rated specifications. An important
test for equipment whose reliability must be
guaranteed, such as an emergency communications
transceiver.
burnout
1. Failure of a conductor or component
caused by overheating from excess current or
voltage. 2. The open-circuiting of a fuse. 3. Electrical
failure of any type.
burst
c
l
Bunet s formula
1. The abrupt ionization of the gas in an ionization
chamber by cosmic rays. 2. An abrupt increase
in the amplitude of a signal. Also, the type
of signal that results from burst action. 3. See
COLOR BURST.
burst amplifier In a color-television receiver, the
amplifier that separates the burst pulse from the
video signals and amplifies the former. See
COLOR BURST.
burst gate timing In a color-television receiver,
the timing of the gating pulse with the input signal
of the burst amplifier.
burst generator A signal generator delivering a
burst output (see BURST, 2) for testing various
types of equipment. Its output is intermediate
between sine waves and square waves, and is
convenient for rapidly appraising the perfor-
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