A radio base station has at least two radio chains and a precoder for precoding information symbols by a precoding matrix for multi-antenna transmission to a number of user equipment terminals. Precoding matrix statistics representative of phase coherency between at least two radio chains is compiled based on feedback information representative of preferred precoding matrix from one or more user equipment terminals (S1). A relative phase error is then detected between radio chains based on the compiled precoding matrix statistics (S2). It is then possible to compensate or otherwise adjust for the detected relative phase error (S3) based on the compiled precoding matrix statistics.