Hybrid TEM-dual surface wave in a coaxial cable

A number of investigations have been published on this subject since the author´s original paper three years ago, and most of them disagree with the conclusion then reached, that a thin coating of dielectric over the inner conductor of a coaxial cable could, in suitable circumstances, bring about a reduction of attenuation. On the other hand, careful experimental work has shown what appears to be behaviour very similar to the original prediction. The present paper deduces relationships between some of the parameters of the cable, by applying the `addition theorem¿ to the relevant Bessel functions whose arguments are of near value, thereby enabling more accurate calculations to be made. The results seem to lend support to the experimental observations.