By Kenneth L. Smith, Times Wire And Cable
A recent publication in the Multichannel News (1), "Signal Leakage Threatens to Cripple Cable Industry," emphasizes the importance of addressing CATV system signal leakage. Excessive egressive signal leakage could lead to fines by the FCC, ban of CATV use of aviation, navigation and communications frequencies. Excessive ingressive interferences signals lead to loss of customers due to poor reception. This paper evaluates drop cable "aging", an important characteristic which has not previously been evaluated on an experimental basis. Cables were removed from systems and evaluated to determine degradation. The cables measured had been in use for various periods of time, up to 23 years. The most significant "aging" observed was a decrease in shielding (increase in rf leakage). This information is correlated with laboratory "aging" tests to allow predictions of long term performance of relatively new drop cables. The test results show that the different drop cable types in use have varying degradation, a maximum of 18 dB compared to the best cable with only 7 dB degradation in 20 years of service. This quad shield cable, adhesive foil-60% braid-foil-40%-braid, which has the lowest degradatior: also has the lowest rf leakage at any point in time. (14 dB to 18 dB lower leakage than the second best).