I've been using twisted pair telephone wire with no problems at all for the last 5 or so years. We tape it to the concrete and put the rug over it. I just buy a spool of telephone cable at Radio Shack, strip the out sheathing and untwist the twisted pair, tape to the concrete and wire nut it to the split comming out of the black box on the coax. I used the same method when I was running our parking lot program at the LHS. In two seasons outdoors I had only one person cut the loop. We puled the tape back, twisted the ends back together and retaped it and we were good to go. I know of other parking lot tracks that do the same thing without problems. Way less expensie then an AMB loop and the wire is thin enough so that 1/12 cars don't ave any issues I've used 22ga in the past but you can fell it under the carpet with a 1/12 car.