A 2-way splitter has 3.5dB of loss.
A 4-way splitter, 7dB.
An 8-way splitter, 11.5dB.
(3-way splitters have a loss that varies depending on which output you are looking at. Two outputs are 3.5dB and one is 7dB of loss, unless you have one of the exceedingly rare equal-loss 3-way splitters. I've never seen one and offhand I don't recall what the loss is for those).
Simply add up the loss of all the splitters in the signal path to get the total loss, and if you are dealing with very long runs of cable you could add in the cable loss too.
Most cable companies seem to feed houses with a signal level adequate for at least a 4-way splitter. My cable company feeds my house with about 14dBmV, so I could use an 8-way splitter to hook up 8 TVs and still have an adequate signal.
You do not want the signal level to drop below 0dBmV because that is generally considered the minimum signal level which will produce a picture with no visible defects. Cable modems will be OK with lower levels, although they suggest no lower than negative 15dBmV. In fact, my brother has a cable modem connected through a 4-way and a 2-way splitter totalling 11.5dB of splitter loss and it works fine. Unfortunately I can't find out how to access the diagnostic webpage for that modem, I'd really like to know what sort of signal level it's getting.
(On top of the splitter loss, there's the cable loss..there's got to be at least 150' of cable between the cable tv pedestal and that cable modem).
[This message has been edited by brianl703 (edited 05-24-2005).]
