This paper discusses the correspondence which exists between the spatial complexity of the antenna of a single frequency detection system and the frequency complexity of a multi-frequency detection system using an antenna of simple spatial nature. Use has already been made of this correspondence in detection methods employing two spaced isotropic receivers to detect wide bandwidth signals. In this paper the concept is viewed from a more general standpoint and extended to the two dimensional case. The use of multiple frequencies to obtain shaped beams and superdirective patterns from two spaced isotropic receivers is discussed.