Calibration of loop antennas at VLF

Abstract

A technique and the equipment used for the precise determination of field strength of signals received from VLF transmitters is described. The equipment, which is battery operated, contains provisions for the reception of VLF signals and the generation of standard fields to an accuracy of 5 per cent. Both the receiving and transmitting antennas are loops. The field strength is determined in terms of a quasi-static magnetic field with the two loop antennas positioned coaxially at a spacing of approximately two meters. Although the technique was developed for use at VLF, it can be used at higher frequencies for calibrating loop antennas, generators, and volt meters, and for determining effective heights of antennas, or similar applications.