a3 whose diagrams cannot be pivoted and have an approximately constant sensitivity within the angular range between t and t 39 indicated in fig1 and 2 the transmission signal s produced in the radar transmitter is fed to the antenna a1 through a transmit receive switch let the antenna a1 in the example illustrated be designed as a phase array antenna whose diagram orientation is determined in a known manner by the adjustment of the phase shifters associated with the individual radiators the diagram is pivoted by adjusting the phase shifter through a phase control device instead of the phased array antenna an antenna pivoted mechanically by a servomotor can also be provided the antennas a2 and a3 are designed only as receiving antennas since these antennas should have an antenna diagram that is not focused or only slightly focused not drawn in fig3 antennas of simple construction such as horn antennas can be used of the echoes reflected to the antenna system only the right handed circularly polarized signal fractions are received by the antennas a1 and a3 and only the left handed circularly polarized signal fractions are received by the antenna a2 and fed to the receiving channels e1 e2 and e3 connected to the antennas for the output signals of the receiving channels the signal levels l1 l2 and l3 are obtained in level detectors b1 b2 b3 the signal level l1 of the signals received through the transmit receive antenna a1 is compared in a first level comparator p1 with the level l2 of the signals received through the receiving antenna a2 the level l2 is preferably valued higher by a constant prescribed factor k.