Cable Plant Training

Basically, the isolation is between the two ports on the splitter. The higher the number the better. It's saying that it would take 140db of some type of signal (off-air, ham radio, etc) before the signal would bleed onto the other port of the splitter.

If there is some type of interference on one leg of the splitter it should not bleed over onto the other leg, unless that signal level reaches 140db.

If there is some type of interference on one leg of the splitter it should not bleed over onto the other leg, unless that signal level reaches 140db.

Cable TV uses a coax network. The signal rides on the inner conductor completely surrounded by the shield. If a perfect world the shield would perfectly isolate the inner conductor from effects on the shield.

EMI isolation, is the amount of noise protection the shield offers. Better shields offer better noise immunity (like a quad-shield RG-6 vs. an RG-59).