Coax tv splitter, 2tvs fine, 3rd off splitter is fuzzy?

I bought a standard dual shield 250ft roll of RG6 coax line to run to the upstairs of a house. currently, there is the main catv line coming into the basement from outside the house. this is plugged into a 3 way splitter - one for a basement tv about 15 ft away(signal is fine), one on the main level of the house about 25 ft(signal is fine) and i now ran one to the upstairs (should be under 50ft when finished). before going any further i just stripped the end and tried it in the closest upstairs tv but this signal was fuzzy. thinking the 250ft roll might be a bit too long to keep a good signal, i cut 4 ft off the end, and took a tv right next to the splitter and used the 4ft line and it was STILL fuzzy. so from this, i can tell its not the splitter's fault (i changed the order of the lines that are plugged into the splitter and that wasnt the problem either). the current CATV line does not have any markings on the cable jacket so i dont know if i am using the same type the was put in previously. the type i put in is rb59 dual shield 3ghz coax. the existing cable lines are just a bit thicker, i dont know if that cable might be quad-shield or rb6 or if there is a way to tell, but after some research i am still stuck. no stupid responses please.