It has been suggested by Ardavan that the coherent radiation from pulsars could be due to current distributions corotating at superluminal phase speeds beyond the speed-of-light cylinder. Similar distributions moving at phase velocities exceeding the speed of light also occur in travelling-wave antennae. Pulsar models satisfying Ardavan's criteria are readily conceived in terms of antenna theory and are found not to give rise to the surprising radiation characteristics predicted by his analysis. Reasons for the failure of Ardavan's model are discussed.