beaded coaxial cable (radio frequency transmission line). A form of coaxial transmission line in which the inner conductor is centered in the outer conductor by a series of beads made of insulating material.
beam (radio navigation). The beam is a descriptive term which refers to an invisible path produced by radio signals. An aircraft can follow the beam when going to or from a navigational fix.
The term beam became popular with the four-course, low-frequency radio range that projected four clearly defined beams, or courses, from each of the transmitting stations. When a pilot was flying an aircraft along one of these courses, he was said to be “on the beam.”
beam (structural member). A long, heavy, metal or wood member in any type of structure used to support both bending and shear loads.
beam antenna (radio antenna). A radio transmitting antenna that concentrates its radiation into a narrow beam. This beam can be oriented in any direction needed.
beam-power tube (electron tube). A form of tetrode (four-element) electron tube that uses two beam-forming electrodes, or plates, to shape the flow of electrons so they travel from the cathode to the plate in definite beams.
The screen grid is wound in such a way that its wires are in the shadow cast by the control grid, and keeping the screen grid out of the path of the electrons helps minimize screen current.
Beam power tubes are power amplifier tubes, rather than voltage amplifiers.
beam resolution (radar technology). The ability of radar to distinguish between targets at approximately the same range but along different azimuths.
bearing (mechanical equipment). A device fitted into a hole to reduce the friction present when a shaft rotates in the hole. Plain bearings are liners for the hole made of a material such as bronze or babbitt metal which have a low coefficient of friction. Antifriction bearings consist of a pair of hardened and polished steel races, with either hardened steel rollers or balls rolling between them.
bearing (navigation). The horizontal direction to one object from another. True bearing is the direction measured in degrees clockwise from true north. Relative bearing between two objects is the direction measured in degrees clockwise from a reference point on the first object, such as the nose of an aircraft, to the second object.
bearing cage (antifriction bearing component). A thin sheet metal separator that keeps the rollers or balls in an antifriction bearing evenly spaced around the races. The bearing cage should never touch either of the bearing races.
bearing cone (antifriction bearings). The tapered bearing races used with some roller bearings.
For wheel bearings, the inner cone is slipped over the axle, and the outer cone fits into a recess inside the wheel. Hardened steel rollers ride between the two cones.
bearing failure (riveted structural failure). A type of failure of a riveted joint in a sheet metal structure. A joint fails in bearing when the metal tears at the rivet holes before the rivets shear.