The antenna developed by Uda and Yagi took the basic three element parasitic array described in the last chapter and extended it, through the addition of multiple directors, to provide a highly focused beamwidth signal for VHF and UHF (the "ultra short waves" in Yagi's article title). They empirically developed the early designs of such arrays, including the optimum lengths and spacings. The results have been relied on for many years, until the availability of modem computer modeling and simulation.