I have several Arduinos networked together using just a single twisted pair wire (signal and ground) that I took from a Cat5 cable. That is I removed all the wires from the cable casing and took the 4 twisted pairs apart and used just a single twisted pair (2 wires). It works fine, even over distances about 25 feet.
I then took an entire cable with all 4 sets of twisted pairs in tact and used just a single pair for the same sort of connection and it failed miserably. Essentially I just wanted to keep the outer cable casing on because I was running this wire up above the ceiling so rather than strip it all and pull out just a single twisted pair, I just used the entire thing.
Because there are now 8 wires is that simply causing much more signal loss along the way? Or is there something else going on here? I'm still only using a single twisted pair of the 4 in the cable. The others are just empty ends.
Thanks.