said by Streetlight:
You should be able to get two two-way splitters from your local Comcast office for free or flag down a truck and maybe get a three way. My local office didn't have any splitters having more than two outlets when I rewired.
Two two-way splitters will give you the three outputs as telcodad showed - two -7 dB outs and one -3.5 dB out.
Yes, if you get only two 2-way splitters (or your cabling arrangement requires two splits in different areas of your home), as Streetlight
suggested, here is how to connect them:
It's best to avoid using an amp if possible. Unless you have a lot of splits to feed a large number of boxes in your home, you should not need to use one.
If the signal levels are low entering your home, you need to call Comcast about that and have a tech check it out.
If after replacing the splitter(s) and cables with high-quality ones, you still have a signal level issue with the farthest TV, then placing a good-quality bi-directional amp right after that splitter output then may help (you want to avoid using an amp on the cable modem's line). Besides the amp that jack b
suggested, you can check out some other ones that were recommended in this thread: http://www.dslreports.com/forum/r26893652-DVR-Which-AMP-to-use