Implementing a passive signal 4-way splitter will technically attenuate the signal.
This might affect the picture quality negatively when:
Solution:
Install an RF signal amplifier in front of the signal splitter, preferably close to the source.
This will ensure the fixed attenuation of the splitter (-7.4 dB) has no effect on the signal quality of the outputs.
Note: the attenuation does not depend on whether there is 1, 2, 3, or 4 outputs connected.