UBE - (See upper band edge.)
ULTRAHIGH FREQUENCY - The band of frequencies from 300 megahertz to 3 gigahertz .
ULTRASONIC - (1) Sounds above 20,000 hertz . (2) Supersonic.
UNBALANCED CRYSTAL MIXER - A circuit consisting of a section of coaxial transmission
line one-half wavelength long that is tuned to the difference (intermediate) frequency
between the local oscillator and rf echo signals .
UNBLOCKED - Having a blocking factor of one logical record per block.
UNDERCUT - (See washout.)
UNIDIRECTIONAL - In one direction only .
UNIDIRECTIONAL ARRAY - An antenna array that radiates in only one general direction .
UNIFORMITY - The extent to which the output remains free from variations in amplitude.
Uniformity is usually specified as the positive and negative deviations from the average
output within a roll of tape.
UNIJUNCTION TRANSISTOR (UJT) - A three-terminal, semiconductor device with a negative
resistance characteristic that is used in switching circuits, oscillators, and
wave-shaping circuits .
UNIT - (1) An assembly or any combination of parts, subassemblies, and assemblies
mounted together. Normally capable of independent operation . (2) A single object or thing
.
UNIT SIZE - The standards adopted to make comparisons between things of like value (for
example, the unit size for conductors is the mil-foot) .
UNIVERSAL TIME CONSTANT CHART - A chart used to find the time constant of a circuit if
the impressed voltage and the values of R and C or R and L are known .
UNTUNED LINE - Another name for the flat or nonresonant line .
UP LINK - The frequency used to transmit a signal from earth to a satellite .
UPPER BAND EDGE (UBE) - The upper band edge of the recorder/reproducer response
(usually at the -3dB point).
UPPER-FREQUENCY CUTOFF - The highest frequency a circuit can pass .
UPPER SIDEBAND - All of the sum frequencies above the carrier .
USER PROGRAMS - Programs written to solve specific user problems, called applications
software.
USERS - (1) The people who use the output from computer processing. (2) The people who
operate a computer for their own purposes.
UTILITY PROGRAMS (UTILITIES) - Programs designed to perform often needed general
functions.
