Losses in a Periodically Gapped Cable Armor in Contact with the Surrounding Soil

A variational method is presented for evaluating the effective impedance of the periodically gapped armor on a buried cable. The armor is assumed to be in direct contact with the surrounding soil, so that the gaps, which are intended to break the longitudinal electrical conductivity, are in fact electrically bridged by the soil. From the effective impedance can be calculated the armor losses and, when the cable is used as a buried antenna, the reduction in antenna efficiency. Numerical results are presented graphically, and some corroborating experimental evidence is reported. Sponsored in part by Naval Electronic Systems Command, Washington, D.C.