TECHNICAL ARTICLE: Moisture: The Enemy

Jan. 10, 2019

There have been reports of TCAS II installations showing signs of RF cable deterioration after only a few years of operation. The cause of these problems has been traced to moisture either in the coaxial cable at the antenna connector or inside the connector itself. Moisture trapped inside a connector can produce effects ranging from unnoticed to serious, depending on the demands of the system. But be assured the cable assembly will be affected if moisture enters. The shields and conductor can suffer corrosion, especially if cleaning is less than meticulous when the connector is applied. However, even if corrosion were not to develop, moisture present in the connector or dielectric can change the characteristic impedance of the cable. Where there is a change in impedance, there is an increase in signal reflection (VSWR). As a result, a sensitive system may become unreliable or, worse, fail.