A high gain antenna (20) that produces a pencil beam along the ground and a lower gain antenna (26) that produces a beam extending above the pencil beam are coupled to a source (2) of r.f. pulses so that the amplitude of the r.f. pulses applied to the high gain antenna (20) is less than the amplitude of the r.f. pulses applied to the lower gain antenna (26) during airplane detection and the full amplitude of the r.f. pulses during a pulse segment is applied to the high gain antenna (20) during wind pattern detection.
