It could also be a bad splitter or patch cable. Make sure they are rated up to at least 1GHZ (1000MHZ), 2.4GHZ is better. The cables should be RG6 and have compression connectors. The splitter needs to be in good condition and good quality. Many cables and splitters sold in big box stores and electronics chains are poor quality and do not work well. Stuff that has been kicking around in a junk box should be examined closely and thrown out if they are worn, damaged or do not have clearly marked, adequate specs.