Cable Television Terms
Ingress is the leaking in of over-the-air television channels into the cable system. This will be most apparent in the NTSC cable channels 2 to 13 which are on the same frequencies as the over-the-air channels. Cable companies try to minimize its impact this by assigning channel guides, pay-tv advertisement and community channel on the channels used by broadcast stations.
However, the problem does not stop there. Any source of interference can leak in and degrade reception, including pager and cellular towers, radio station transmitters and pesky neighbors with illegally boosted CB radios. Personal experience: Cheaper networking equipment can produce an interference signal spanning many channels, channels 2 to 6 being particularly sensitive to it. Any spark-generating device (household appliances) will produce severe interference that will show up as well.
Coaxial cable is not unlike plumbing: Bad junctions leak, bad pipes burst: To get rid of (okay, minimize) ingress, make sure all the cable end f-connectors (screw-on) are in good shape, not loose, no exposed wires. If broken go to an electronics store and have them refitted professionally (about $5 a crimp for silicon-sealed weatherproof, accept no less). Low grade cabling spanning several dozens of feet will allow ingress, replacing it with higher grade RG6 will help. Inspect all the cables in their entirety to check for damage.
Disclaimer: IANACTT