For a grounding wire larger diameter wire works better and also not having any sharp bends, kinks, or loops in the ground wire is better. The reason for this is because of surges from lightning strikes. If lightning strikes nearby surges of current can travel outward in the ground from the location of that strike. If such a surge happens to come to your dish you want it to travel down the ground wire instead of traveling through your LNB and down your coaxial cable. If your gorund wire is really small or has kinks, loops, or sharp bends in it, the inductance (and thus impeadance) of it will be higher and the pulse from the lightning strike may find it easier to travel through your LNB and down your coaxial cable than to travel down your ground wire. Inductance of the grounding wire is important because a pulse from a lightning strike will have a very fast sharp rise time and inductance is kinda like electrical inertia in that it opposes very rapid changes in current flow. So, if the inductance of your grounding wire is too high the pulse will look for easier paths to follow.