A technique for transmitting reference signals (RS), from a first station using a transmit antenna (400) with a number of antenna ports to a second station for determining channel state information (CSI), of a radio channel between the first station and the second station is described. As to a method aspect of the technique, a first set of precoders (502) is defined for the number of antenna ports. Based on the first set, a second set of precoders (702) is derived for the number of antenna ports. A second rank of the second set of precoders (502) is different from a first rank of the first set of precoders (702). The second rank of the second set is less than the number of antenna ports (402). Each of the antenna ports is associated with non-zero energy by at least one of the precoders (702) of the second set. The RS are transmitted using each of the precoders (702) of the second set.