I am looking for a couple of boxes to put in my son`s rooms .would i need a booster box .I have already got a box down stairs .Can you run thee boxes of one cable and can you run a box of the modem cable
Depends on how strong your signal is. I run 4 receivers and broadband off one feed and all work fine, you will need a splitter similar to below to split the cable feed. Only buy what you need, dont have any unused sockets on the splitter.
If you want to run 2 boxes and 1 broadband you will need a splitter like this, 2 sockets for receiver 1 for BB, single one is your feed.