Problem is, even with a PIC with a 40Mhz clock, the quickest interval you can measure is 100nS. In the cable i'm using, signals travel at 71% the speed of light. Which means 100nS equates to 56.8m. Obviously thats nowhere near the resolution required. To measure within 1m i'd need a clock speed of 2.2GHz - Obviously not going to happen on a pic.

Im wondering how the hand-held cable testers manage that kind of timing.