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 [18].
UNIDIRECTIONAL
In one direction only [1].
UNIDIRECTIONAL ARRAY
An antenna array that radiates in only one general direction [10].
UNIJUNCTION TRANSISTOR
(UJT)—A three-terminal, semiconductor device with a negative resistance characteristic that is used in switching circuits, oscillators, and wave-shaping circuits [7]
UNIT
(1) An assembly or any combination of parts, subassemblies, and assemblies mounted together. Normally capable of independent operation [17]. (2) A single object or thing [13].
UNIT SIZE
The standards adopted to make comparisons between things of like value (for example, the unit size for conductors is the mil-foot) [4].
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 [2].
UNTUNED LINE
Another name for the flat or nonresonant line [10].