This paper presents an experimental investigation of the performance impact of two important PHY layer design options that arise in 802.11 ad-hoc networks. In particular, throughput results are provided for multi-hop ad-hoc networks with and without PHY auto-rate control and for single vs. multiple frequencies. The study is motivated by the fact that default 802.11-based ad-hoc networks using commercially preset auto-rate PHY and a single frequency channel suffer from performance degradations caused by link quality fluctuations and MAC layer self-interference respectively. A baseline ad-hoc network scenario is set up on the ORBIT radio grid testbed at Rutgers and is used to determine end-to-end multi-hop flow throughput with default rate control and single channel operation. These results are then compared with those obtained with multiple channels and alternative PHY-rate selection methods demonstrating the potential for significant performance improvements. We observed significant improvements in end-to-end flow throughput, as much as ∼4x for multiple channel vs. single channel and ∼3x for optimally controlled PHY rate vs auto-rate.