The Reducticn of Interference to Medium and High Frecuency Receiver Aerial Systems in Ships

In ships the restrictions on aerial sites lead to the use of common aerial working systems, while below decks the concentration of large quantities of electrical and electronic equipment produces a high level of environmental noise. The combination results in severe interference problems, and the need for special precautions in system design and installation integrity. After briefly describing such a common aerial working system and the main precautions taken, the paper indicates that the performance depends to a great extent on the integrity of the aerial feeder systems. It shows how the difficulties of installation and maintenance have resulted in a change from the traditional lead sheathed co-axial cable to one with a convoluted copper outer. At the same time aerial lines within receiver offices were changed to braided co-axial cable and new aerial line filters and switches were designed for the system. Some measurements indicating the degree of screening effectiveness obtained in a ship installation are presented.