The degree of dynamics with respect to changes of the network's topology strongly affect the performance of a wireless mobile ad hoc network. Main reasons for topological changes are (i) node mobility and (ii) wireless radio fluctuations, e.g., due to fading effects. The impact of node mobility on ad hoc network performance has already been studied intensively. However, these studies usually do not consider temporal fluctuations of the wireless channel. In this paper we quantitatively study the impact of radio fluctuations on the performance of wireless ad hoc networks. Based on field trial measurements of IEEE 802.11b wireless LAN communication in a static line-of-sight scenario, we derive a basic model for non-deterministic but temporally dependent received signal power variations. According to the derived model we quantify the impact of radio fluctuations on topological change rate (TCR) and link stability as relevant ad hoc network performance metrics via simulation. The effects of pure node mobility and the effects of signal strength fluctuations as well as the combination of node mobility and fluctuations are studied. We demonstrate that signal strength fluctuations have a significant impact on ad hoc network performance metrics sometimes 'outoperforming' the impact of node mobility. Thus, non-deterministic radio fluctuations cannot be ignored when designing robust ad hoc network protocols based on ad hoc network simulation and analysis.