One of the problems with discussing this topic is that nearly all studies of radials deal with 1/4 wave verticals. Most ham stations including mine don't have the luxury of a height of 130 feet.
There are many cases where some "novel" grounding scheme is touted as "just as good as 120 radials" and indeed it may be for the 1/4 wave height case. What is scarce is advice for the owner of a short vertical as to what to do about grounding. What grounding scheme would it take to make the proverbial 43 foot vertical play as good as a 130 foot vertical? Whatever that scheme is, we know that it will have very narrow bandwidth. This is a good litmus test to separate short vertical installations worthy of additional testing from low efficiency ones. Of course, narrow bandwidth is merely necessary, but not sufficient, to prove high efficiency. The advantage of the bandwidth criterion is that it is easily and unambiguously measured, as opposed to field strength. The bandwidth should ideally be determined by measuring the antenna drive impedance directly, rather than looking at it through a matching network. A matching network will to a greater or lesser extent decrease the bandwidth of the antenna. Alternately, the matching network can be modeled to remove its effect on bandwidth. I think it is less likely that you can be fooled by a bandwidth measurement than you can with base impedance measurements. Rick N6RK _________________ Topband Reflector