An apparatus for measuring the magnitude of an electric field having an antenna open to the field. The antenna is connected to a data converter which generates an output signal proportional to the magnitude or power of the electric field detected by the antenna. The data converter provides an output signal to a memory unit which stores the magnitude of the electric field. The data converter and memory unit are contained within a housing and the antenna protrudes outwardly from that housing so that the housing and antenna may be positioned within the area of the electric field.