Aerospace Glossary Letters U - Z


UF – Thermoplastic underground feeder and branch circuit cable.
UHF – Abbreviation for Ultra High Frequency, 300 to 3,000 MHz.
UL – Abbreviation for Underwriters Laboratories, a non-profit independent organization, which operates a listing service for electrical and electronic materials and equipment.
UTP – Unshielded Twisted Pair cable.
Unbalanced Circuit – A transmission line in which voltages on the two conductors are unequal with respect to ground; e.g. a coaxial cable.


VDE – German Society of Engineers that establishes standards and testing requirements.
Velocity of Propagation – The speed of an electrical signal down a length of cable compared to speed in free space expressed as a percent. It is the reciprocal of the square root of the dielectric constant of the cable insulation.
VHF – Abbreviation for Very High Frequency, 30 to 300 MHz.
Viton – DuPont trademark for a series of fluoroelastomers based on the copolymer of unylidene fluoride and hexafluoropropylene.
Volt – A unit of electromotive force.
Voltage – The term most often used in place of electromotive force, potential, potential difference, or voltage drop to designate the electric pressure that exists between two points and is capable of producing a current when a closed circuit is connected between two points.
Voltage Rating – The highest voltage that may be continuously applied to a wire in conformance with standards or specifications.
Voltage Standing Wave Ratio (VSWR) – The ratio of the maximum effective voltage to the minimum effective voltage measured along the length of a mis-matched radio frequency transmission line.
Volume Resistivity – The electrical resistance between opposite forces of a one cm. cube of insulating material, commonly expressed in ohms-centimeter.
VW-1 – A flammability rating established by Underwriters Laboratories for wires and cables that pass a specially designed vertical flame test, formerly designated FR-1.