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eat note • Be0 69
beat note The sum or difference frequency that results
from the heterodyning of two signals or, under
some conditions, of more than two signals.
beat-note reception 1. Reception in which a radio-frequency
carrier is made audible by heterodyning
it with a beat-frequency oscillator (BFO) to
produce an audible beat note. 2. Superheterodyne
reception (see SUPERHETERODYNE CIR-
CUIT).
beat tone A beat note in which the frequency is
within the range of hearing.
beaver tail A flat or elongated radar beam, wide in
the azimuth plane. Primarily used to determine
the altitude of a target. The beam is moved up
and down to find the target elevation.
Becquerel effect A phenomenon in which a voltage
is produced when radiant energy, such as infrared,
visible light, ultraviolet, or X-rays, falls on
one electrode in an electrolytic cell.
bedspring A directional antenna consisting of a
broadside array with a flat reflector and one or
more helical driven elements.
beep A test or control signal, usually of single tone
and short duration.
beeper 1. A pocket- or hand-carried transceiver—
especially one for maintaining two-way contact
with personnel who are away from their base. 2.
An acoustic transducer that produces a beep in
response to an input signal.
beetle A urea formaldehyde plastic used as a dielectric
material and as a container material.
bel Abbreviation, B. The basic logarithmic unit
(named for Alexander Graham Bell) for expressing
gain or loss ratios. One bel is equivalent to a
power gain of 10. Also see DECIBEL.
bell An electric alarm device consisting of a metallic
gong that emits a ringing sound when it is
struck by an electrically vibrated clapper.
Bellini-Tosi direction finder A direction finder in
which the sensing element consists of two triangular
vertical antennas crossed at right angles,
the antennas being open at the top and accordingly
not acting as conventional coil antennas.
bell-shaped curve A statistical curve (so called
from its characteristic shape) that exhibits a normal
distribution of data. Typically, the curve describes
the distribution of errors of measurement
around the real value.
bell transformer A (usually inexpensive) stepdown
transformer that operates an electric bell or similar
alarm or signaling device from the ac power
line.
bell wire Insulated 18-gauge (AWG) solid copper
wire, so called because of its principal early use
in the wiring of electric-bell circuits.
belt generator Also known as a Van de Graaff generator.
A very-high-voltage electrostatic generator,
a principal part of which is a fast-traveling
endless belt of dielectric material. At the lower
end, charges of one sign are sprayed on the belt
at 10 to 100 kV dc and are carried to the inside of
a hollow metal sphere at the upper end, where
they are removed and spread to the surface of the
sphere, which they raise to a potential up to several
million volts.
benchmark A test standard to measure product
performance.
benchmark routine A routine designed to evaluate
computer software and/or hardware, producing a
good indication of how well the software or hardware
will perform in real-life situations. In particular,
tests instructions per second and
throughput, thereby producing an indication of
the overall computer power in applications, such
as word processing, database, spreadsheet,
graphics, animation, and mathematical calculations.
bench test An extensive checkout of a piece of
equipment in the test laboratory—either to find
an intermittent problem, or to check for reliability.
bend An angular shift in the lengthwise direction of
a waveguide.
bending effect 1. The downward refraction of a
radio wave by the ionosphere. 2. The lowatmosphere
turning of a radio wave downward by
temperature discontinuity and atmospheric inversions.
Benito
A continuous-wave method of measuring
the distance of an aircraft from the ground, involving
the transmission of an audio-modulated
signal from ground and the retransmission back
to ground by the aircraft. The phase shift between
the two signals is proportional to the distance to
the aircraft.
bent antenna An antenna that has its driven element
bent, usually near the ends and at right angles,
to conserve space.
bent gun A television picture tube neck arrangement
having an electron gun that is slanted to direct
the undesired ion beam toward a positive
electrode, but which allows the electron beam to
pass to the screen. This prevents the ion beam
from “burning” a permanent spot on the phosopor
of the screen.
Be0 Formula for beryllium oxide. Also see BERYL-
LIA.
Cathode
Control
grid
Ion trap
magnet
First anode
bent gun
Second anode
Electron
beam