ABSTRACTMeasurements of E-plane radiation patterns of flanged H-plane sectoral horns are given. Apart from the two unkown parameters, viz. the flange length and the included angle, a third factor‘the position of the flange’is proved to have a very significant role in controlling the E-plane patterns of the H-plane horns. Broadening and narrowing of the beam are possible by a single flange of fixed angle, by adjusting its position from the open end. The essential conditions for these are derived theoretically and experimentally varified for four horns of different parameters. Measurements are given for a number of flanges in each case and for comparison, patterns are plotted when each flange is kept at the aperture and at the newly suggested positions.