Nonagreement of forward echo and return loss

Mathematical models of coaxial cables allow the derivation of relationships between the forward echo and return loss due to the periodic nature of the structure. Experimentation has served to demonstrate that the prediction of forward echo from return-loss information is limited in its application for practical cables. This is mainly due to the fact that coaxial cables do not always exhibit truly periodic structures. In the letter, we present results that indicate the disagreement that can occur in practice.