Malcom Technical Support
ICOM and Kenwood Repairs
Working on getting it here. bear with me.
Cold water pipes are only good grounds if you can attach to them within a foot of where they come in from the earth, otherwise it is a radiator. Round wire is generally only a "adequate" (i.e. marginal) ground for up to 8 feet, maybe 10. One of the biggest mis-conceptions about RF grounds, is the bigger the wire the better the ground. Which is actually totally inaccurate. The size of the wire (in any service) is current.. the bigger the wire the more current. Since ideally RF grounds have almost no current (mostly voltage) a big wire isn't helping that much.
It is true that a bigger wire (#12 compared to 00) the bigger will work better (usually) but it is still "round" Round to RF is an inductor. Given the length, and diameter of the wire (assuming it is straight) it takes on an inductance. Usually 10 feet and longer, ends up being resonate at 15 or 10 meters! The AT500 and usually the 2KL will be difficult to function that way. (actually I'll bet the 2KL trips the protection on 15 and 10)
It is best to use "flat strap" It doesn't have to be high tech, just conduct. I used to use galvanized chicken wire (1/4 mesh) on boats. Cheap and easy to use. The general rule is the longer you go, the wider the strap needs to be. 1/2" is usually good to 10 feet, 1" to 15 feet, more than 15 feet, you really should use 3" min. The strap doesn't have to be thick, it's the surface area that is important. Believe it or not, household foil works quite well up to 20 feet. Only draw back is it is fragile. For short runs, I would recommend, the shield from a old piece of RG8, squish it flat, tack solder it every 6 inches or so to keep it flat.
If you are just no where near a good ground. The 2KL will give you trouble, it demands a good ground. If you are on the first floor, and have access to under the floor, but not through the wall, put a ground rod under where the radio is. I know, not easy, but it's allot better than a long wire under the floor.