I have dish and was thinking of getting cable internet. I want to know will the internet use the same cable that Dish uses, with a splitter at the end of course?
You can use the same type of cable RG6, but not the same cable you are already using with Dish.
The cable company is supposed to run a new RG6 cable to connect to your internet modem. This new cable can be splitted for use with another CableTV box or a VOIP from the same Cable company.
You cannot use a diplexer with Cable and Dish. It can cause interference in the CableTV's signal in your area.
You do not want to use a diplexer for cable Internet. You really want to run a cable directly from the drop to the modem where possible for best results.
Make sure that all tvs work when the cable guy leaves. A common problem is that the cable co's think that the lines in the house belong to them. They will cut your dish lines to use for the cable modem. Make them run an extra line for the modem and have them tell you how and where they intend to run the lines before the work is done.