A far-field radio frequency telemetry (RF) system for communicating with an implantable medical device includes a diversity antenna system. An antenna control circuit selects one or more antennas of the diversity antenna system for reducing potential data transmission errors associated with nulls encountered by the telemetry system due to environmental reflections of RF electromagnetic waves. In one embodiment, a different active antenna is selected when a transmission failure deemed to be associated with a null is detected. In another embodiment, a new antenna is selected on a regular basis to reduce the probability of encountering a null. In another embodiment, the telemetry system includes multiple processing paths each associated with one antenna of the diversity antenna system, and a different processing path is selected when the transmission failure deemed to be associated with a null is detected.