  Three years ago, the report of a solitary radio burst was thought to be the
first discovery of a rare, impulsive event of unknown extragalactic origin
(Lorimer et al. 2007). The extragalactic interpretation was based on the
swept-frequency nature of the event, which followed the dispersive delay
expected from an extragalactic pulse. We report here on the detection of 16
pulses, the bulk of which exhibit a frequency sweep with a shape and magnitude
resembling the Lorimer Burst. These new events were detected in a sidelobe of
the Parkes Telescope and are of clearly terrestrial origin, with properties
unlike any known sources of terrestrial broad-band radio emission. The new
detections cast doubt on the extragalactic interpretation of the original
burst, and call for further sophistication in radio-pulse survey techniques to
identify the origin of the anomalous terrestrial signals and definitively
distinguish future extragalactic pulse detections from local signals. The
ambiguous origin of these seemingly dispersed, swept-frequency signals suggest
that radio-pulse searches using multiple detectors will be the only experiments
able to provide definitive information about the origin of new swept-frequency
radio burst detections.
