We focus on improving primary radio link reliability as the key to allowing the construction of large reliable and efficient WSNs spanning regions with heterogeneous and time-varying environmental conditions. We have built a new platform with two independent radios operating at well-separated frequencies and spatially separated antennas, demonstrating that their combination can protect against communication loss from multi-path fading and environmental interference. Operating multi-radio platforms requires additional energy when using naïve implementation of low power listening protocol. We developed a new MAC layer protocol that combines synchronous LPL with automatic selection of LPL check intervals. Our evaluation demonstrated a substantial increase in the operational lifetime and mean power consumption over existing protocols in single radio networks and even more in dual radio networks.