This paper presents the FPGA implementation of a multiple antenna wireless communications system based on Alamouti's transmit diversity scheme. Alamouti's transmit diversty scheme is a space-time block code with support for two transmit antennas and an arbitrary number of receive antennas. Our implementaiton demonstrates this space-time code in a system with two transmit and just one antenna at the receiver. In addition to implementing the encoding and decoding algorithms described in Alamouti's paper, we have designed and implemented additional subsystems necessary to establish an end-to- end link over real wireless channels. These systems, described in detail below, address the challenges of timing synchronization, carrier offset recovery and channel estimation. When combined with an implementaiton of Alamouti's code, these designs form a complete multiple antenna wireless communications sytem.