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282 Field Day • fil
Field Day In amateur radio, an annual contest
sponsored by the American Radio Relay League
(ARRL) to simulate emergency communication
conditions. It occurs during the last full weekend
in June.
field direction The direction in which an electric
field or magnetic field exerts its force.
field effect The phenomenon in which the flow of
current carriers in a solid substance is controlled
by an external electric field. A useful application
is the FIELD-EFFECT TRANSISTOR (FET).
field-effect tetrode Also called dual-gate FET. A
field-effect transistor (FET) in which the gate electrode
is split into two parts, each connected to a
separate external lead. The reverse bias between
the channel and either gate lead affects the conductivity
through the device.
field-effect transistor Abbreviation, FET. A monolithic
semiconductor amplifying device in which
a high-impedance GATE electrode controls the
flow of current carriers through a thin bar of silicon
(rarely, germanium) called the CHANNEL.
Ohmic connections made to the ends of the channel
constitute SOURCE and DRAIN electrodes.
Also see JUNCTION FIELD-EFFECT TRAN-
SISTOR, METAL-OXIDE SEMICONDUCTOR
FIELD-EFFECT TRANSISTOR, and CHANNEL
JUNCTION FIELD-EFFECT TRANSISTOR.
field-effect varistor A nonlinear dual-terminal
semiconductor device capable of maintaining a
value of current for a range of voltages.
field-emission microscope An instrument for examining
the atomic structure of high-meltingpoint
metals; it magnifies more than 2 million
times. The metal to be examined is made into a
needle that is subjected to 5 to 30 kV; electrons
emitted by the tip of the needle form an image on
a fluorescent screen.
field forcing A method of controlling a motor by
changing the magnetic field in the windings.
field frequency In television, the product of frame
frequency and fields per frame (in the United
States, 60 per second).
field intensity 1. The strength of an electric or
magnetic field. 2. The strength of an electromagnetic
field, usually expressed in microvolts per
meter or millivolts per meter.
field-intensity meter See FIELD-STRENGTH ME-
TER.
field ionization The tendency for atoms to be ionized
in a gas by a high-intensity electric field. The
ionization occurs mostly near the poles of the
electric field.
field-ion microscope A high-resolution field-emission
microscope that uses helium ions instead of
electrons. The ions are repelled by the tip of the
metal needle under observation, forming an image
on a fluorescent screen. Also see FIELD-
EMISSION MICROSCOPE.
field length Record field size in applicable units,
usually bytes, characters, or words.
field magnet 1. The permanent magnet in a dynamic
speaker. 2. A similar magnet in an earphone,
generator, microphone, motor, phono
pickup, transducer, etc.
field pickup 1. A probe or sensor for insertion into
an electric or magnetic field. 2. An on-location radio
or television program (i.e., one coming from
outside the studio). Also called remote or NEMO.
field resistor A resistive component consisting of
an insulated form with a thin layer of conductive
material.
field rheostat The rheostat whose setting determines
the amount of current flow through the
field coil of a motor or generator.
field scan A form of television scanning in which
the lines are scanned alternately.
field-sequential system A color-television system
in which the image is reproduced by means of primary
color fields (red, green, and blue) flashed sequentially
on the screen of the picture tube.
Compare DOT-SEQUENTIAL SYSTEM and LINE-
SEQUENTIAL SYSTEM.
field strength See FIELD INTENSITY.
field-strength meter An instrument for measuring
the radio-frequency (RF) voltage of a signal
reaching a chosen location. The instrument consists
essentially of a radio detector equipped with
a portable antenna and an output meter.
µA
field-strength meter
field telephone A rugged, portable telephone system
for outdoor use.
field test A test of equipment under actual operating
conditions (i.e., outside the laboratory or factory).
field winding See FIELD COIL, 1, 2.
fig. Abbreviation of figure (usually in reference to
an illustration).
figure-8 pattern 1. A bidirectional antenna pattern
whose cross section, in a specified plane, resembles
the numeral 8. 2. A Lissajous figure
resembling the numeral 8.
figure of merit 1. For a capacitor, inductor, or
tuned circuit, the ratio of reactance to resistance.
Also called Q factor or Q. 2. For a magnetic amplifier,
the ratio of power amplification to control
time constant. 3. For a transistor, the gain-bandwidth
factor.
fil Abbreviation of FILAMENT.