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The angular width of a radar beam, horizontal or vertical, the power of which is measured at the half power points.

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ASME SECTION I

Power Boilers.

SPREAD

The divergence of the air stream in a horizontal or vertical plane after it leaves the outlet.

GROWLER

A piece of ice smaller than a BERGY BIT or FLOEBERG, often transparent but appearing green or almost black in color. It extends less than 1 meter above the sea surface and its length is less than 20 feet (6 meters). A growler is large enough to be a hazard to shipping but small enough that it may escape visual or radar detection.

HALF-POWER POINTS

Power ratios used to define the angular width of a radar beam. One convention defines beam width as the angular width between points at which the field strength is 71 percent of its maximum value. Expressed in terms of power ratio, this convention defines beam width as the angular width between half-power points. A second convention defines beam width as the angular width between points at which the field strength is 50 percent of its maximum value. Expressed in terms of power ratio, the latter convention defines beam width as the angular width between quarter- power points.

HALF-POWER POINTS

Power ratios used to define the angular width of a radar beam. One convention defines beam width as the angular width between points at which the field strength is 71 percent of its maximum value. Expressed in terms of power ratio, this convention defines beam width as the angular width between half-power points. A second convention defines beam width as the angular width between points at which the field strength is 50 percent of its maximum value. Expressed in terms of power ratio, the latter convention defines beam width as the angular width between quarter- power points.

HOUR-GLASS EFFECT

A radarscope phenomenon which appears as a constriction or expansion of the display near the center of the plan position indicator, which can be caused by a nonlinear time base or the sweep plot starting on the radar indicator at the same instant as the transmission of the pulse. The phenomenon is most apparent when in narrow rivers or close to shore.

GYROSCOPIC DRIFT

The horizontal rotation of the spin axis of a gyroscope about the vertical axis

HORIZONTAL EARTH RATE

The rate at which the spin axis of a gyroscope must be tilted about the horizontal axi

INTENSIFIER

A device which converts low pressure fluid power into higher pressure fluid power.

ANSI-B.31.1

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