The calibration of four-aerial adcock direction-finders

The paper describes how it is possible to determine the minimum radius at which a four-aerial Adcock direction-finder may be calibrated for instrumental error without introducing spurious effects due to the proximity of the calibrating transmitter to the direction-finder. It is shown that this minimum radius depends upon the spacing of the aerials, the wavelength, and the inherent accuracy of the direction-finder to be calibrated. In most cases of practical interest the minimum radius is found to be between 0.6 and 3.5 Such distances, while usually easily attainable on the short-wave band, may not be possible in the case of medium or long wavelengths.