Sentence:  The antenna patterns and the power <WSD>gain</WSD> at the peak of the beam were both measured ( Mayer , McCullough , and Sloanaker , 1958 b ) , so that the absolute power sensitivity of the antenna beam over the solid angle of the moon was known . 
Meaning of the word marked with <WSD> tags:  the amount of increase in signal power or voltage or current expressed as the ratio of output to input