this amp do not work with the latest cable modem such as Motorola sb 6120 . the amplifier definitely boost the tv signal as I can verify that signal-to-noise ratio increase from around 32 db to 40 db . however , the amp seem to either block full bi-directional communication or filter out require frequency for the cable modem to make online connection to isp -lrb- in my case Comcast -rrb- . furthermore , the vendor 's -lrb- cabletvamps.com -rrb- 's support be a joke . when I ask why it be not work with my cable modem , the reply be a copy\/paste of some unrelated topic about the amp not support satellite tv and I should return the product . Main reason I purchase the booster be to split to both cable modem and tv without drop signal strength to the cable modem , but that be not possible with this junk . I be back to use a simple -3.5 db splitter that support upto 1,000 MHz Update ! - the CableTVAmps support finally reply : quote : `` the Motorola s2 be a passive return unit - these be not design to be use with Cable Modems as they will not support the signal . you will need a active return amplifier -lrb- the Motorola k4 be a 4-port unit -rrb- which will support a Cable Modem and any interactive service -lrb- OnDemand , etc. -rrb- that the Cable Company offer ''