Hi Kenneth,
Lanny is correct, the Minelab SD series works very well in really bad ground because these detectors do have a ground balance system.
However, what constitutes bad ground to a VLF is not necessarily "bad ground" to a PI. In other words, there is areas people call bad ground where a PI without a ground balance system will work quite well.
A VLF simply doesn't like magnetite, or heavy black sand deposits, while a PI, even without a ground balance will produce little if any signal from this type of mineralization. This is where a PI really excels.
Now, I am not sure where you mean when you refer bad ground in North Central AZ, but I just got back from AZ. While there, I hunted in the general vicinity west of Mayer and found the ground to be quite quiet on my PI. Yes, there was a lot of black sand in many areas, and the sides of the hills were rocks or mainly decomposed granite. In this area, my PI was very quiet. So, one such as the GQ should be fairly quiet. There will be some ground response, but nothing like one can expect in other areas. BTW, this is the general area where I found my two smaller nuggets.
I have a DD coil on my PI and that really helps, but have hunted similar areas with a mono coil and found the ground conditions to produce minimal response even with a mono coil.
Where I have experienced a much stronger ground signal is out on the flats just south of Octave where the ground is quite red and has a heavy composition of clay. At this location, the ground signal can be quite strong if you are using a mono coil. In this area, a ground balance system would definitely be better, but a DD coil really helps also.
In a nutshell, it is really difficult to answer your question specifically. Also, one should realize that a very sensitive PI will produce at least some ground response in most areas. Just how much is difficult to say. What I have found is the more clay in the soil, the greater the response. The more gravel or black sand, the less the ground signal.
Even with that in mind, one shouldn't expect a PI lacking a form of ground balance to be as easy to use as another with ground balance. Of course, there is a significant difference in costs between the two also.
Reg
