The bottom of the ring is 13 inches off the ground and there are no RF absorbing materials close by. It dips fine and makes contacts but just doesn't seem to be as strong as other antennas. I have a ground screen on the ground under the antenna which consists of welded wire fencing (hog wire).
2011 Update: I gave this antenna away before I had a chance to do much more with it. I don't know if I could have ever gotten it to work better.
2015 Update: I borrowed this antenna back from the person I gave it to and used it for a year. It is a good performer and is probably the equivalent of a dipole. It is not a strong dx antenna, due to takeoff angle. Modelling it with EZNEC shows only moderate low angle radiation. It would have to be raised to a half wave off the ground and turned horizontal to achieve more dx.