I would think solid copper wire would work, but my favorite for grounding is braid. I usually get mine from RG-8 or RG-11 coax but there is no reason why braid from RG-58, 59 or coax similar would not work. I just happen to have a lot of old coax laying around that I don't care to rely on for RF use.
73, John, W4AWM ************************************** Get a sneak peek of the all-new AOL at http://discover.aol.com/memed/aolcom30tour