Better to use an existing drop (and buy a 2nd cable modem), or to add a splitter after the existing modem?

Question

Need to hook up a 2nd computer at home. Not worried so much about cost as about signal strength.

Answer 1

I don't think your cable company will let you have multiple cable modems connected directly to the cable, since you've only got a single account thus a single "real" dynamic IP.  What you would add to existing modem is not a splitter but a gateway/router.  These can be had for $50-100 depending on if you need wireless or not and they almost always include a few ethernet ports for you to connect local machines to.  This will also improve your security if you currently have your computer connected directly to your modem.

Answer 2

I suggest if cost is no issue that you hire the work done as you really are hardly aware of what you are describing.

You should buy a router, connect the Internet feed from the modem to the router WAN port via wired CAT5 cable and then connect all pcs via wired CAT5 cable.  No CAT5 cable should exceed 100 meters in length as this is the recommended signal maximum.

If you need to exceed 100 meters, use media converters to convert the ethernet signal to a Fiber signal, use fiber to run the long haul, and then another media converter and then CAT5 cable.

You never "add a splitter" in a computer network.  This is not like runing an analog voice phone line.

You never talked about or suggested wireless links.  These can be added but this is where signal strength can be an issue.