right, ok like someone mentioned before. cable signals travel on waves like most other types of signals we humans perceive with our senses. the further the signal travels on its wave the more it loses quality (if left to its own devices). this is called "attenuation".
so you got a couple options on how to resolve it. you can get a device which uses electrical current to boost the signal. a signal amp. you can stop being a cheap fucker and at least have the sense to spend money on decent cabling (since you are getting service for free), i personally recommend highly shielded RG6 cabling. you could also make sure your splitter is a high quality splitter with a good signal to noise ratio (SNR). you could check for loose fittings (the shiny steel thing at the end of the cable wire). you could be a badass, climb up the pole and change out the splitter up there since its likely been there for quite some time..
best of luck,
yr friendly neighborhood cableguy.