1) if you use two cables and only have two devices, you do not need a network switch. Although a 5 port unmanaged switch is only about £10 or £12!
2) Need more info on what type of cable your brother is splitting?
3) Network Switches do not impede Ethernet net signals at all, if could be said that they boost them. If you wish to run a cable over say 600m you would put a switch in the middle because you cannot go over 305m.
Very good tough external Ethernet cable is expensive out £120 for 300m or 0.50p per metre. I just use trunking behind my downpipes and internal cable as I had a lot spare.
Tudor There are 10 types of people: those who understand binary and those who don't and F people out of 10 who do not understand hexadecimal c1a2a285948293859940d9a49385a2