The Average Axial Magnetic Field of a Loop Antenna

It is shown that the average magnetic-field intensity normal to a circular area coaxial with a thin current-carrying circular loop is proportional to the average current around the loop. Thus the constant-current assumption often associated with the calibration of loop antennas is unnecessary. The result is generalized to provide a method of calculating the average magnetic-field intensity normal to a circular area in a plane parallel to that of an arbitrary shaped thin-wire conductor carrying arbitrary current.