Magnetic Field for Radiating and Receiving Loops Placed on Parallel Planes

In the calibration of radio receivers and field-intensity meters, a radiating loop and a receiving loop under test are mainly located either in a coaxial or coplane to each other. A formula to obtain the average magnetic-field strength incident on a receiving loop is derived for the case where the radiating and receiving loop antennas have a certain deviation on a parallel plane from the coaxial or coplanar alignment of the loops. In order to expand the uniform region of the magnetic field around the test point, the distribution of the magnetic field is investigated by using this formula for some alignments where the four (or less) radiating loops and a receiving loop lie on parallel planes to each other. It is obvious that the uniform regions are improved by factors of about 10 or 16 by increasing a radiating loop to two or four loops, respectively.