The term "artifact" is not germaine to NTSC composite video. The cable distance and gauge as well as shielding and surrounding environment can all play a part in degradation of the signal. This can be seen as ghosting, loss of luminance, contrast etc.
As S-video signals on HO equipment are rarely hefty enough to function as a driver for long cable runs, a distribution amp is generally used. What kind of distance and using what cable?