There is provided mechanisms for determining complex weight vectors. A method is performed by a radio transceiver device. The method comprises obtaining measurements of reference signals. The reference signals are transmitted by another radio transceiver device by applying precoding weight vectors in a sequential order at an analog antenna array of said another radio transceiver device. The precoding weight vectors as well as the sequential order are known to the radio transceiver device. The method comprises determining channel estimates for each individual antenna element of the antenna array by using the measurements in combination with knowledge of the precoding weight vectors and the sequential order. The method comprises determining complex weight vectors to be used for subsequent data transmission from said another radio transceiver device based on the channel estimates. The method comprises providing an indication of the complex weight vectors to said another radio transceiver device.