this item cause some deterioration of cable modem signal , as do most other signal amplifier . some amplifier even have warning not to connect to a modem . recommend use a two-way splitter in the input signal line prior to connect to this amplifier . one output of the splitter should be directly connect to the cable modem , via rg6 or rg59 cable , entirely bypass this amplifier . the other output of the splitter should be connect to the input of the amplifier and the outlet of the amplifier connect to the various tv cable . be sure to use a 75 ohm terminator for unused outlet . the amplifier work great on tv signal , reduce graininess , pixel freezing , and improve picture quality , on both analog and digital signal .