From memory standard cat5 cable is not screened, its simply 4 sets of twitsted pairs. You might be better off using some form of screened cable like this



From the website http://www.homestead.co.uk/productca...tegoryid=51023

100% overall foil screened multicore cable manufactured to UL2464
100% overall foil screened multicore cable with drain wire and PVC outer sheath. Enables data to be transmitted over longer distances. Suitable for RS232 applications. 7/0.2mm tinned copper conductor, PVC insulated. Conductor resistance 79Ohms/Km, voltage rating 300V, temperature rating 80'C.
Send data over longer distances using twisted pair cable. Conductor resistance 79ohms/km, voltage rating 300v,temperature rating 80'c.