I made a cable last night using UTP CAT5e to test for differences in cable interference. There is no difference as far as I could tell between the CAT5e cable and the cable provided by URC. In both cases I got the same interference regardless which cable I used.

I will try testing again with STP CAT5/5e/6 when I can get my hands on some cable. I have tons of UTP at work but no STP. I don't know when I will get around to making another cable but I will post my findings here after my next round of tests.