Methods, systems, and devices for wireless communication are described. An access point (AP) may switch antenna array configurations during reception of a packet to determine channel characteristic information for the antenna array configurations. The AP may use the channel characteristic information to select an antenna array configuration for use, and to determine a beamforming steering matrix for the selected antenna array configuration. In some cases, the AP may use multiple antenna array configurations to transmit training fields in the preamble of a packet. The AP may receive channel characteristic information for each of the antenna array configurations. The AP may use the channel characteristic information to select an antenna array configuration for use, and to determine a beamforming steering matrix for the selected antenna array configuration.