An anomalous effect in HF curtain arrays

Discusses an effect which was discovered during the re-engineering of one of the BBC´s HF transmitting sites. During the commissioning of the first array (a wideband, four-stack array) an effect was noted which gave rise to reflection coefficients of greater than unity in two of the stacks. This, if the array had been operated without any modifications, would have led to breakdown. Similar problems were observed in arrays which were subsequently erected by antenna contractors. It was found that by changing the feeder lengths it was possible to avoid (but not eliminate) the problem.<>