The performance of co-located WiMAX transmitter sites operating at 2.5 and 3.5GHz are compared, based on coverage assessments. The study showed that the 2.5GHz performed marginally better than the 3.5GHz under the same RF conditions and clutter environments. In general, the 2.5GHz was found to provide slightly better coverage at the edge of the cell, with an average of 2dB less loss at lkm from the transmitter location. Comparisons of the path loss difference between these two frequencies with various empirical propagation models (COST-Hata, ECC-33, WINNER II-Suburban, SUI Flat) were made, and differences from 2.9 dB to 6.2 dB are reported from these models, which are much larger than those reported here (around 2 dB for outdoor). These differences are also dependent on the distance to the site. Indoor penetration loss was found to be around 1 dB.