The impact of transmit-antenna spacing and signal-to-noiseratio on channel capacity has been measured intensively in a variety of scenarios. When looking at the physical layer throughput of a multiantenna communication system, the behavior over antenna spacing may look completely different, leading to other conclusions regarding the optimal antenna distance.In this paper, we compare -by testbed measurements-the closedloop throughput of a standard compliant 2×2 IEEE 802.16-2004 WiMAX radio link with the unconstrained capacity and the mutual information of the channel. Results are presented for base-station antenna spacings of 0 wavelengths (cross polarization) as well as spacings between 0.6 wavelengths and 7.7 wavelengths (equal polarization).