The effect of mutual impedance on the spacing error of an eight-element adcock

An eight-element Adcock array has the advantage of reduced spacing error as compared to four element arrays of the same size. If this error is calculated when the mutual impedances between elements are neglected, spacing error curves result which are poor approximations and may not be attainable in actual measurement. New relationships are derived for the two-phase eight-element array which include the effect of mutual impedance. Curves are plotted to show that earlier published values for the angular spacing between elements are probably too high to result in the best performance. It is shown that the value of which results when the mutual impedances are neglected may result in an appreciable spacing error. It is apparent that the selection of an antenna becomes quite important since the mutual impedance is determined thereby. Evaluation of the error in a particular case will depend on the antenna selected. It is also shown that, if the goniometer impedance is high, the spacing error will be reduced.