Ingress Interference to Signals the Cable TV Distribution Networks.

When direct reception at home is possible from different TV transmitters, the ingress interference will become a problem in coaxial cable TV distribution networks. However, the signal quality should then be high in the cable distribution network. The cable TV frequency plan shall be selected such that the ingress interference will have negligible subjective effect on the picture quality. In this study this is realized by incrementally related carriers with a frequency offset against standard frequency plan. Each viual carrier is phase locked to one component of the set of reference frequencies. At the same time, this principle allows improvement in intermodulation such as carrier to composite triple beat ratio as desired in multiple channels network with harmonically related carriers. The permitted interference field strength can be estimated with the help of data on shielding factor of installation material and of home receiver. Thus, the frequency plan can be determined for the cable distribution system. The data are provided on the Basel cable TV distribution project as example.