effective earth radius
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effective earth radius[ə¦fek·tiv ′ərth ‚rād·ē·əs]
A radius value used in place of the geometric radius to correct for atmospheric refraction in estimating ranges of antennas when the index of refraction in the atmosphere changes linearly with height; under conditions of standard refraction it is ⁴⁄₃ the geometric radius. Also known as effective radius of the earth.