Splitting cable - degradation of signal

( former cable tech )

i would not add a 4th splitter as you will lower the signal coming in and will raise the return        ( signal going out ) .          for internet a modem is happy with the forward signal at -8 to +4 and the return level you don’t want to go any higher than 52......it can go to 54-55 but that is really pushing it.       if the return level is to high, then this is where you will see pixels and streaming will have issues.         

then you have to also look if you run the line yourself, if you don’t do correctly, you could cause noise out on the plant, which in turn would cause your neighborhood to have issues and you could actually cause an outage.

there is more.....but this is just part of it.

you can add a amp which will increase the tv signal, but you don’t want to have the internet line amplified.      what they will put before the amp is a dc or two splitter and one leg of the dc would feed the modem and the other leg from the dc / splitter would go to amp / splitter for tv.

i don’t suggest you do the amp as you could easily cause the issues that i mentioned earlier .  your cable company can easily have the lone installed, verify levels are good and if a amp is needed, then they can put one in

if a tv outlet is connected to a splitter and the tv is not on , it is still active per say and signal is effected.....as all you have to do is turn the tv on and you have tv.